No period for 5 months negative pregnancy test what could be wrong?

Hi.I need help please. I hope you find time to read and respond to it.

Im 21, i have irregular period, usually it occurs once every two months. I last had my period around the last week of December 2015 and i never have it again since then. I had sex on february so Im worried that i might be pregnant so i took an hpt last april but it came back with negative result. i took another test around the first week of may and its still negative, that gave me sort of relieve since im not feeling any pregnancy symptoms at that time.
I became sexually active since i decided to live with my boyfriend last may 23. We are doing it everyday without using any contraceptive (not even withdrawal) cause we want to have a baby. I am feeling signs of pregnancy for about a week now, (sore breast with ugly veins and darker nipples, nausea, vomiting, craving for food, unusually hungry, too weepy, increased urinating, tired and sleepy all day) i took htp last week, and its still negative.

2 days ago, i felt cramps on my lower abdomen but its not as painful as when i had my period and there is a spot, i know its blood but its brownish not red. Still feeling the cramps until now, but i still dont have my period, and im still feeling all the symptoms, i dont know what to think. Is it possible that i am pregnant or its just all in mind?
Is it possible that i ovulated and got pregnant even though i never had period for 6 months already?
Any answer will be higly appreciated.

Hi im 22 years old. I'm always having regular period until Mar. 05,2016. I still have sex with my husband every week. No vomitings but really gained a lot of weight. from 50 kilos now im 60kilos(first time). i always maintain 50kilos but now it just keeps gaining. though i only eat once a day. pregnancy test all negative. went to the doctor four times had vaginal check up but was all negative they even put some medicine to my vagina so my period comes out. but until now still no period. Do i have a possibility of pregnancy? stretch mark all over my legs and
some in my breast. sleeps a lot than usual. i would be very happy if i was pregnant thought. until now still confuse.

Hi I'm 45 yrs old had a normal period every 28 days, had my last period Nov. 8,2015 all pt results negative. March 1,2016 had a very light period lasted 1day, April 20,2016 had my trans vaginal ultrasound result I'm not pregnant. But I notice my tummy is getting bigger, again June 19,2016 had my period light so I went to my ob for check up she ask me to have another tv ultrasound, I took pt again this morning but got negative result. Please help been drained with check ups already am I pregnant?

Hi. Im 22 . I always have only 3 days menstrul period but on irregular dates and only light period not even using pads . Ive been havin this abnormal period just only last year . Last feb my period ddnt showed up but i got it at first week of march for only 3 days and its lil heavy than which i thank coz i get back to normal and uses pad . But last April my period ddnt shows up until now so im 3 months delayed . Im thinking i was pregnant till i tried the test today. The pt shows negative. I had sickness. Sore nipples. Wnting to pee every minute. Loses weight but tummy got bloated. My situation now confuses me. Need help

My period is usually normal.I had sex in January.Then my period is normal.I took primolut N to delay my period in March.In may my period is twice.First lighter and second spotting.Now in June period is not started.what was happening with me?