one year pp and period randomly disappears but not pregnant?

DS just turned and year old and is still BF he does eat solids and just recently was night weaned. (about 3 weeks ago) my husband and i started trying again in January. i was due for my period on the 25th and still have not started. ive taken three test and they have all been negative. my first pp period was 7 months pp and the first 3 were a little irregular but i was no more than a week late. and the last few have been right on time. so im confused as to why now all of the sudden im so late?

I would go to the doctor and get a blood test.