Why Am I Miscarrying Again And Again?

My husband and i have now been pregnant twice within the past 5 months and have miscarried both times. Why is this happening? We are 25 and 23 and neither of us smoke and we only drink on occasion. The first time I miscarriage we were 7 weeks along and it completed 2 weeks later. This go around I wasn't even 4 weeks and we miscarried. Should I have some testing done? I have a tipped uterus, but that's as far as my knowledge of any problems goes. I would think that since it's so easy for us to get pregnant that we are healthy enough to carry a baby full term, but so far this isn't the case. Why is this happening?