Lack of oxygen at birth can have no or negligible effects, moderate effects and disastrous effects. It's a wild card and research in the area is interesting but clinical findings are unpredictable. It's possible you have brain damage, which can be assessed through various diagnostic imaging techniques, although I don't see that happening for you unless a doctor is willing to go out on a limb, if you have one hell of a large wallet or participate in a research study.

It's best to avoid asking friends or family as to whether you have a particular psychiatric illness, especially if they don't have formal training or much education in that area. They may very well be correct, however, it strengthens self-diagnosing and that can be a temporary roadblock if you do see a psychiatrist. Additionally, if you see a psychiatrist and get an alternate diagnosis, you may be left wondering who to trust: the clinician with years of formal training who met you for less than a couple of hours or family and friends who lack such training but have known you for years.