Cycle day 51 with no period after stopping birth control

Ky 8-15-17👼🏼 & 10-28-17👼🏼 Pregnant with my🌈💕
I am now on cycle day 51 with no period. September 20th I started taking birth control. I quit taking birth control in January after I finished my pack for that month to see if I am regulated yet. Then February 7th I got my first period after being off of birth control. I still have not gotten my period for March which is now cycle day 51. I had symptoms like I was going to get my period (mild cramping in the abdominal region and near belly button, gassy, slight pain in breast, and my body felt really warm) but it never came. I was also having alot of milky/creamy cervical mucus but it seems to be going away. I took a pregnancy test two weeks ago which was negative and I took one over the weekend and it was negative. I don't understand why I got my first period after being off of birth control on time in. But now I still have not gotten my second one??? And I'm on cycle day 51. We want to start ttc for our 1st time soon but can't do that untill I have my period.