I don't think you can ovulate right before your period, but if you have a very short luteal phase, maybe a week before.
Or maybe your periods have regulated and you just haven't detected LH yet. If you have a 33 day period, it could be day 16 or 17 before you see the surge.
Stress can definitely throw your cycle off, it can also lead to no ovulation.
I think its possible, but uncommon. if you do ovulate right before your period, you would have a luteal phase defect (ie, a very short luteal phase) If i recall correctly, anything under 10 days is considered short for your luteal phase. If you do find you are having a short luteal phase, get to a doctor quick, because if you are TTC, it can cause issues. Hope thats not the case for you though. :-D
The best way to figure out if you are ovulating and when you are ovulating is to chart your basa body temperatures. If you google it there is tons of info on it.
Good luck.. sorry about your m/c