If you go for 90 dys without your period perhaps you are not ovulating. You should talk to your doc and check what's going on.
I last had my period on nov. 30 2007 and haven't have one again, we did like 6 pregnancy test, even at the doc. office all was negative, but since he is just a reg. doc. he wasn't able to drawn my blood and test it. o so that's what he said, my tummy has increase since nov. but I don't have any symptoms, I'm going crazy, and my boyfriend keeps on telling me how unhappy he is with me because i can't give him a child. see my situation is a little dif. than everybody I had my tubs tide before now I untide them and was preg. 3 times 2 natural missca. and one ovarian preg. the doc. had to terminate the preg. and now I don't know what to do.
Do you know for sure that you ovulated on Jan 1st? Do you use ovulation prediction sticks or monitor your cervical mucus? 90 days is a long time to go without a period. I guess I'm confused about your question. Are you pregnant right now and trying to find out the conception date or are you trying to figure out when you ovulate so you can concieve quicker? You have to be careful with those online fertility sites b/c a lot of times they are not accurate b/c everyone's cycle is different.