-It's a commandment (It's written "Do not forsake the gathering of the Brethren"-The Bible)
-For edification (Through the Word,Worship,Praise,Prayer)
-Coporate Anointing (Where two or more are gathered in my name,I am in their midst).
I go to Church mostly for the first and second reasons though .
Sister,I do not condone fornication but I'm encouraging you to go to Church with your boo. You don't need to runaway from Church because you are "Sinning" Infact that's when you need God more.The word of God sanctifies .
The Flesh doesn't get born again that's why you see many "born-agains" struggling with a lot of Sin not just fornication.Its ok to fall once in a while and repent of your sins but what's not ok is "PROUDING"in Sin.Making Sin a lifestyle is a no no and shouldn't even be mentioned amongst believers.
All we ask for everyday is for God to help our areas of weaknesses. That's why the Bible encourages us to renew our minds on a daily basis.Christainity is not a religion per say but a way of living.Its a day to day conscious living and examination of oneself striving to be like our master Jesus Christ.
Instead of condemning yourself and him why don't you ask the Holy Spirit to help you to be chaste.Since you are stronger than him in faith why don't you say no to him with the Word and also stop sleeping over at his place or encouraging moments that will lead to sex.In our Lord's Prayer there's a part that says "....and lead us not into temptation".
Jesus prayed that prayer and was like us tempted too.So as far as we are alife, temptation will always come.
I am not encouraging anyone to wallow in Sin cos of Grace neither am I judging anyone.All I have been trying to say is,Don't run away from Gods prescence because of your sins, run to him and he will cleanse you.