Help20

Hey I new to these. I'm 21 years old I have been with my girlfriend for 3 year next mount will be our 4 year anniversary. I really do love, but know my head his telling me that I don't love here and don't won't to be with her. And it really depress me and give me anxiety. Let me go back and tell you how this all started. 3 mounts ago I was at work and gay thought poped in my head and i got depressed and anxiety and I been battle that every since then, but the orther day my girlfriend, her roommate and I was going to mall and they was play fighting. Then a thought poped in my head that they had something going on and then BOOM! That's with the thoughts can that I don't love her and I don't won't to be with her. Like I don't know what to do anymore. Before I was having all these crazy thoughts (me being gay and me not loving my girlfriend) I was on top of the world I was sooooo happy. I wanted to get my degree and marry my girlfriend and start a family. I'm so confusted right now. So do I have rocd or I'm falling out of love with my girlfriend????