thoughts?

so i am 18. i had never have a penis near me until may 22/23rd of this year. my bf wore a condom and only put part of his tip inside of me. felt a little pressure but it didnt hurt (felt good) i made him stop because i wanted to wait longer for my first time (some would say im no longer a virgin though). he told me he never came nor did he precum and there were no holes in the condom after he took it off. the second time we got intimate (may 24/25) i gave him oral sex until he ejaculated i swallowed the cum then after taking me home later that night we had phone sex (we both masturbate over the phone until we both cumulative, it was an hour after the oral sex and i did not wash my hands prior to being on the phone ). since the incidents i have stressed about being pregnant (took 3 pregnancy tests, all negative but one was invalid)

dates of test: june 16th (invalid), june 18th, and july 1st.

i expected my cycle june 20th and it never came..my bf tells me to stop worrying but at this point i am three weeks late. i missed my period completely for the months of march and April without any sexual activity other than masturbation

. i was in school at the time so it may have been stress (i was a senior so graduation was approaching ). should i be worried?