positive antibodies

Hello. did anyone ever test positive for antibodies. baby is at negative all other tests and sono appts look good. I am 15 weeks. I now have to take blood tests once every month and ultra sounds every two weeks for the time being. I just took a blood test today letting me know how much antibodies there is.. which I will find the answer out next week. it is so odd to me because I never had this issue with my first (which is now 10 months) and I have never had any blood transfusions.. ugh.. I don't know what to think :(:(:(:((