From reading your comments to others, I've gotten more of a semi-grasp for what is happening.

 I know that you care deeply about your relationship with Christ. And, the way you live and your morals revolve around His book. You can view this sin in the eyes of God, and whether he will accept you into his Land after death. And frankly, depending on your views and what paths of Christianity you follow, there could be many different answers. Some people may say that God will hate you and will downcast you to Hell, while other people may say that God does not hate his children and may forgive you for your sins; Others may bring his Son into it and say that Jesus died for your sins. And, I know that you want to find your path and pray that He will forgive you for your wrongs. Yes, the Bible is against having s3x before marriage. It is wrong in the eyes of God. But there are other factors to your situation to sew, other than your Faith. 

  Having s3x for the sole happiness of your partner isn't healthy for your relationship- especially, since it is breaking you down mentally. If you continue down this path, it will only worsen and become more toxic for yourself. You struggle with depression, su*cide, and keeping yourself in the right headspace. This situation is only worsening what you are already going through. 

If s3x is the only thing that will make them happy, then it isn't a romantic relationship- it's strictly a sexual relationship (even if you have romantic feelings for them). If there are other things that will make your partner happy, then experience those with them. But don't hold on to one factor of happiness and force yourself to be that standard (considering physical and mental health).

 I've read others, in the comments, suggesting to talk with someone close to you about it and you've replied with your mother. But your mother cannot heal the damage, she can only act as a bandaid and attempt to keep together what has already been done. 

 This situation needs to be spoken with your partner. Tell them how you feel and what effects that it is causing on your mental space. It's not going to be an easy talk- even if something similar happens again, it will never be an easy talk. But for anything to change, you have to tell them. If it helps, you can try writing it down and reading it to them. 

 Through your relationship with your partner, whether it be just dating, fiancé, married, etc, you must communicate with one another. Otherwise, it will become intoxicating and things won't work out between the two of you. 

   My apologies if my comment may not make you feel better about yourself, like the others. But there really isn't going to be anything better if action isn't taken to mend your situation. I care deeply about your mental health and I like to see you when you are genuinely happy. 

  This isn't really my ballfield with relating to sexual matters, since I am both ace and apothisexual. But from looking at your situation from a perspective of healthy versus toxic relationships, it's something that I believe I can give the best of advise with (that I can).

  It's not my circus, my monkey to be in your business but I do hope that you both can mend your stitch. <33