help? opk confusion

Ciara
I had a miscarriage feb 12th. Hcg levels were at 0 by the 14th. I have been doing opk tests and I got flashing smileys from the 25th all the way to the 12th of march when I got a solid.. a solid again two days later on another test. I'm so confused! I feel totally crampy and my doctor told me I'd get my period before now. 
I've used opk before to get pregnant and it was totally normal. This time seems so off? Could I be pregnant again already? Or am I really having a lh surge this far away from my MC?  
Any info helps!