Trying to conceive after miscarriage.

Okay so I'm 23 and I lost my baby at 9 weeks in August. I had a d&c.  Ever since then we've been trying to conceive but it's just not happening yet. My periods are all so irregular so it's so hard to pin point ovulation. Before the miscarriage my periods were like clock work. My last cycle was 21 days but straight after my predicted ovulation I started having brown discharge and this lasted all the way until my period. I know I'm not pregnant because I got a positive on a ovulation test. Has anyone else had this problem?