I’ve Not Seen My Period For About 7weeks Now, Yet I’m Still Not Pregnant

I am in a confused state, needs advice on what step to take next.

The whole thing begins on 25th July when i had unprotected sex with my bf. before then my last period came on the 17th of July. so i had sex just about a week after.

Since then uptil now i have not seen my period. Initially I worried i may be pregnant but after several urine and blood test it all turns out negetive. what could be wrong here? This is the first time i am experiencing this.

I have ran 4 test myself using pt test strips. but all came negative. A day ago I went to a private lab and my blood and urine samples were used for pregnancy test, it still came out negative.

Abeg any medical expert or any one with past experience should assist with advice on next step please.

Note, my boyfriend is aware of the whole situation. he himself is in a confused state. plus I am 23 yrs old just incase my age will help in the diagnosis.