Pregnancy-unexplained bleeding?

I am 17 weeks pregnant , last LMP was 08-03-10. I have had spottingon april 29 which lasted for few hrs. Since then I have been inserting crinone 8% once at night.At week 13 I had extreme shooting contraction like pains in the left groin for a day after which i bled the next morning with dark colored clots.I was hospitalized and was given intravenous duvadilan drips for 48 hrs. The bleeding stopped in few hrs of hospitalization & pain after few days. The sonography showed a healthy baby and os closed.All blood tests were carried and reports were normal.I m continuing with duvadilan twice a day, crinone gel once at night ga in case of gastric, prenatal & shell cal (both given from 24 june),also i was on moderate bed rest, cervix birth c mesured 3.1 cms. on 16 weeks scan as against 3.7 on week 13.Again on 28 I got cramps this time milder and the doctor adviced duvadilan at intervals of 8 hrs and rest and it has helped so far.As per doc there is no evident reason for bleeding as everything is normal. The pain i get is over an inch place from left side of mid genital to the thigh join making left leg heavy and painful.NOtes:-I have undergone a disc prolapse surgery in 2005 for S1-L5 where i felt numbness in left leg.-i have gone for appendix operation at 5 yrs age-i had itp for few months at the age of 9 yrs and its completely cured.-i conceived normally within 1 month of plannning-my anomaly scan and triple test results are also normal.-I HAVE A FIBROID of 45*42 mm in anterior wall on lower part.-placenta is anterior-tlc was 13.8, rest thyroids,sugar everything is normal-I had 4 days before the bleeding, can it be the cause-i bled when i switched to susten instead of crinone.questions:-what could be possible reason for bleeding and pains-how much is the chance to carry to term,-should i be on bed rest, is my cervix length within range, i am only 5 ft in height-in which organ am i witnessing pain?-can i go for normal delivery-is there chance of preterm labor, how to avoid it.i am highly stressed as i want to have this child.