As a Scorpio, i consider sex to be a vital necessity in a relationship. It is a healing and binding factor. Therefore i want to highlight and devote a full page onto understanding where a disappointing sexlife is rooted. Many factors come into play when digging for an answer onto the absence of some good sexual soulmerging in your relationship.
It’s important to understand the problem first out from a realistic perspective.

Causes (Reality – Psychology) 

• Asexuality
• Psychological issues & disorders
• Malnutrition
• (Sexual) Shame
• Low self-esteem
• Eating disorders
• Abusive relationships
• Lack of hygiene
• Physical distance
• Impotency
• Menopause
• STD’s
• Difference in fetishes

1) Birthchart

The importance of sexual activity can be found back in your own birthchart and in those of others. Some people naturally don’t have a strong urge for sex. Are you a sexual person or not is where you should start your search for answers.

Your sexual style
Your sexdrive
Your sexual orientation

The responsible houses 
2nd house = Sensuality & self-esteem
5th house = Romance & pleasure
8th house = Sex & intensity

The responsible planets 
Mars = Sexdrive, stamina & Style
Venus = Sensuality & Love style
Lilith = Sexual issues

Depending on the sign & house placement your sexual style and focus can be found

Sexual shame 
Commonly seen with Virgo placement such as :
• Mars in Virgo
• Venus in Virgo
• Moon in Virgo
• Chiron in Virgo

2) Synastry

A good sexual chemistry in the Synastry chart is seen through the aspects between two people, dependent on various factors. The main indications :

• Moon-Moon
• Moon-Venus
• Moon-Mars
• Moon-ASC
• Mars-Venus
• Mars-Mars
• Mars-Pluto
• Mars-ASC
• Venus-Venus
• Venus-Uranus
• Venus-Pluto
• Aspects between 5th & 8th house
• ASC & it’s ruler

Aspects in Synastry 
Hard aspects between the sexual indicators of two people can cause a huge amount of attraction at first, but may cause sexual issues on the long run. In some cases hard aspects can be beneficial (Venus opposite Mars) , in other cases it completely vanishes the existence of intimate attraction towards eachother. The following aspects contain : Conjunction, Square & Opposition

Mars in hard aspect 
• Mars-Saturn = Restriction, one is hot when the other isn’t
• Mars-Mars = Friction, clash of ego’s
• Mars-Pluto = Power struggles
• Mars-Lilith = Sexual shame
• Mars-Moon = Sensual differences
• Mars conjunct/square Southnode = Weakened sexual desire
• Mars square ASC = Physical aggression

Hard aspects to ASC, 5th, 8th ruler 
• Saturn = Restriction, coldness
• Mars = Aggressive approach, ego-driven
• Neptune = Different sexual ideas and fantasies
• If person A’s 5th house ruler is in hard aspect to person B’s 5th or 8th ruler
• If person A’s 8th house ruler is in hard aspect to person B’s 5th or 8th ruler

Lilith as indication of sexual issues 
Lilith is a strong sexual asteroid and hard to satisfy. When there are a lot of hard Lilith aspects in a synastry chart in indicates two things :
• Strong sexual attraction
• Sexual healing is needed, but might be awkward & painful to go through

Conjunctions of Lilith to the sexual planets are strongly felt at first, they create a huge amount of sexual attraction which to some is overwhelming & intimidating.
• Mars conjunct Lilith
• Mars conjunct Pluto

More on Lilith in Synastry 

Good sex in the beginning, shitty sex near the end 

One planet that’s responsible for this is Uranus. A good example is :
Venus trine/sextile Uranus
Mars trine/sextile Uranus
which in fact is a good aspect to have, depending on how both individuals are.
It ignites an adventurous and exciting beginning which weakens over time. This is the aspect of one-night stands. However, as said before ; it depends on the individuals. If one of you loves a steady sexlife without much kink, this could play out in 2 different ways.
The Uranus person could expand your sexual horizon and you learn to become more openminded towards sexual experimentation, or the Uranus person gets bored of your steady approach.

Neptune is responsible for the fairytale-like energy between two people when it makes a harmonious aspect, which to some it may last a lifetime, but when it’s in hard aspect it could seem like a beautiful illusion at first, but reality kicks in on the long run.

3) Composite

Sexual chemistry in the composite chart is seen through various factors.

• Aspect between 5th & 8th house ruler
• Aspect between Venus & Mars
• Hard aspects From Saturn to Mars or Venus
• Moon in 6th
• Chiron in 5th or 8th

Something i have noticed along the researches i have done, is when the 8th house falls into Capricorn. Maybe it’s coincidence maybe not, since the signs are not necessary important in a Composite chart.
Having Saturn in the 8th house is a strong indication of sexual delay of some sort.
• Sexual coldness
• Physical distance
• Sexual Karma

Hard aspects 
• Saturn-Mars = One is hot when the other isn’t, different approaches
• Saturn-Venus = Lack of selflove, difficulty in expressing affection
• Saturn-Moon = Creates depressive feelings & emotional distance
• Saturn-Pluto = Highly karmic, heavy influence of sexual issues
• Mars-Moon = Friction within emotions
• Mars-Uranus = Nervousness, a to direct approach (no foreplay)
• Mars-Pluto = Power issues, ego conflicts, abuse, intimacy fear
• Moon-Pluto = Overwhelming, intimacy fears & blockages
• Chiron-Mars = Sexual shame & hesitance
• Chiron-Venus = Awkward feelings towards intimacy
• Chiron-Moon = Emotional issues
• Chiron-5th ruler or 8th ruler = Awkward feeling in sexual approach
• Lilith-Chiron = Uncomfortable exposure & energy around sex & past wounds

4) Transits

Transit can be a huge influence on your current sensual needs. They can amplify or weaken your need for intimacy depending on which transiting planet is aspecting your birth planets.

Transiting planets in hard aspect to birthplanets Venus & Mars 
• Saturn = Restrictions, coldness, distance, obstacles
• Venus = Friction, different needs & aesthetic
• Mars = Friction, aggression, egoism
• Uranus = Change in sensual needs
• Neptune = Unrealistic sexual expectations, cheating
• Jupiter = Restricted in sexual expansion
• Pluto = Painful transformative restrictions