I never had a normal conversation with a guy where I find myself comfortable about,and now is worst because I started feeling the uncomfortable sensation means that I like guys,even if I know that I dont. I am lesbian and this disturbs me so much.

OCD loves to look for “evidence” that we do or don’t belong to a specific sexual orientation. It’s looking for certainty. It’s important to notice the things we might be avoiding as a result. Do you avoid spending time with guys? These might be areas you can do exposures. Practicing letting yourself feel that uncomfortable feeling without neutralizing it by doing compulsions such as reassurance or trying to “prove” anything can help you learn that these uncomfortable feelings eventually pass without you having to do anything.