Do fornication and other sexual sins cause damage later in marriage? My girlfriend and I have grown up in Christian families, but we haven't followed our parents teachings, and we ended up in sinful relationships. I had a long term relationship with a girl and we have had sex. My current girlfriend had a few boyfriends before me. I want to marry my girlfriend and I told her my intentions, and she agreed. There is temptation every day, and I fight hard against unclean thoughts.
There are several problems that arise from fornication. It isn't that these problems can't be overcome, but you should be aware that they cause you extra work.
First, as you and your girlfriend's past relationships demonstrate, few couples committing fornication stay together. The reason is simple: there is no hard commitment to make the relationship work, so when difficulties arise as they are bound to do, the couples split because it is the easier thing to do. This attitude of leaving when things get hard is detrimental to a marriage, where an attitude of "we'll make this work somehow" is imperative. It is for this reason that couples who have committed fornication are far more likely to have their marriages end in divorce that couples who wait until marriage to have sex.
Second, fornication introduces an element of doubt. If you aren't able to control your sexual desires before marriage, then why would you do so after marriage? In other words, if you don't think sex is something special that is to be reserved only for a husband and wife, then there will be concern when you are faced with temptation.
A more minor issue is that having sex with multiple partners can leave a person with unreasonable expectations. Every person is different, but we tend to see current events in the light of what happened in the past. Both good and bad memories can cause a person to expect what probably will not happen. There can also be feelings of competing with past partners.
But the most important thing for a marriage is to have God at the center of it and your lives. You don't want to start off on the wrong foot with feelings of guilt that you didn't obey God's commands. "Marriage is honorable among all, and the bed undefiled; but fornicators and adulterers God will judge" (Hebrews 13:4). You both had too much of that in your pasts.
Treat this woman different from your past relationships. She is someone special and someone you want to spend the rest of your life with. So make the wedding special and the wedding night something you both look forward to sharing.
Thank you for your answer, it really helps me a lot. I understand that I still have flaws on this specific subject, but I'm intending to do as the word of God says in Romans 12:2 "And be not conformed to this world: but be ye transformed by the renewing of your mind, that ye may prove what is that good, and acceptable, and perfect, will of God." It's not easy but I'm on it.