I don’t know what’s happening

Let me start by saying I’m 19 and according to my doctor and gyno I have no medical problems. I have been actively trying to conceive for the last 2 years. 1 year with my ex fiancé and this last year with my current boyfriend. I’ve taken prenatals, preseed lube and done about every trick in the book (leaving the Sperm in after sex, elevating my hips, different positions, orgasming with the sperm still in after sex, etc.) I CANT GET PREGNANT!!! I’ve gone to my doctor and OB to address my concerns and they have ran about every test they can besides a papsmear (bc I guess they can’t do that til I’m 21) every test comes back negative for any fertility problems or and medical condition at all. They keep telling me that there should be no reason I can’t get pregnant but I just can’t. I’ve never had regular periods since I first got my period at 13. They are irregular with severe debilitating cramps and about every symptom you can get. They range between 28-48 day cycles. But according to my OB everything is fine. I’ve gone to 2 different OBs and both have said the same thing. I’m terrified that I just can’t get pregnant at all and it’s eating me inside. I want more than anything to get pregnant but I just can’t seem to get it right. Everyone around me is getting pregnant on the first try and I can’t even get one positive test in 2 years, I’m young why is this happening.