I feel like this happens often. I have also been in a long term relationship since I was 16, now 22. Most couples go through communication problem bouts. For me, from my relationship experiences sometimes you just have to lay it out all on the table in one day and work through everything. You can't get lazy and fall off and forget to communicate. I think sometimes we don't want to admit a lot of problems that we see or feel in our relationships. If there is still a lot of love between you two, then what I recommend is having a honest conversation about everything. It's worth a try. The sex thing, is more tricky and it might be rooted deeper. I feel like she has more to say, because she couldn't even verbally say it. I know for awhile in my relationship I was feeling insecure sexually, nothing to do with my SO, just myself and it was affecting our sex life and so when things started being different we had a talk and now it's a much better process. I just didn't want to admit or talk about how I felt for awhile and my SO could tell something was up and eventually I broke down and we talked it over. There might be something deeper going on with her that she isn't ready to talk about yet, but I would recommend just making an effort to communicate with her first and not pushing her sexually until the communication problems are cleared up. Possibly treat her to get away for a night or day or try and do something fun to bring the romance back. Bring her flowers home and tell her how much you love her and want to work things out, etc.