Could I be pregnant? Abnormal period?

Ok, I am 29 - not a 14 yo with no clue - no offense. I have had a lot of problems with my menstruation over the years and have had a lot of tests to rule out PCOS etc. My periods are irregular - they come when they want to. Sometimes I can go 10 weeks between cycles. This used to concern me but not anymore - they come when they come. They are usually very heavy and extremely painful. I can't move on the 1st day and have been in hospital because of it. This time I am in pain but it is different. The pain is more an ache than a stab and my periods - well they are almost nonexistent. I have 'spotted' for 6 days now - completely out of the 'norm' for me. I have always had extremely heavy flow and this is concerning. I have been told that it is unlikely (not impossibly though) that I would get pregnant without IVF so my partner and I don't use contraceptive - he doesn't ejaculate inside me but that's it..... So, is there a chance that I have defied the odds and am pregnant or could this be something else? I don't want to have a pregnancy test and suffer the horrible disappointment that I have had in the past unless I really have to.....