On The 1st Day Of My Due Period I Experienced

On the 1st day of my due period i experienced a gush of clear vaginal fluid for about a day or 2 which was followed my a white mucus type fluid. I have experienced nausea (not soo much anymore), in addition to pelvic pain and left shoulder tip main (which still comes and goes).... I'd like to mention I have taken a pregnancy test 4 days after my missed period which was negative!
Previously I have visited the gp numerous times as I had irregular periods amoungst other things but to no help at all and so have been put off going... the irregular periods have returned after a pretty regular cycle of 28 days. I also would like to mention I get regular pelvic pain and am able to feel ovulation pain every month... please help!