Late period (tired of going through this)

I am 18. I’ve been having sex since i was 16. I’ve been with the same guy for almost 3 years. & we go long distance. There’s one problem we’ve been having for the longest that’s really starting to tire me- pregnancy scares. I’ve had SO MANY. I’ve had like 5 or 6, & it’s because every time we have sex my period is late. My period is like clock work. day 30-31 every single time. but when my boyfriend gets home & we do the whole thing, my period is late by like 3/4 days every time. this leads me to be terrified of the whole pregnancy thing & it causes immense stress. Our sex is 100% protected every single time. We had sex almost 2 weeks ago & behold i am late. I’m late by 2 days. Barely any cramps, my boobs are a tad sore, and i bought two pregnancy tests, cheap care one brand & i told one yesterday & one today but in the afternoon, not the morning. They’re super hard to read. Pregnancy tests always have a tinyyyy faint line 100% of the time for some reason. One part of me is nervous but another part of me is just tired of this. Birth control, no birth control, this happens every single time & it always leads to me to take pregnancy tests. I’ve had friends pick some up for me, i’ve taken them in target bathrooms, i’ve taken them at home. You’d think i was TTC, but it’s like… every single time i have sex my period decides to dip on me & as an 18 year old full time job, going back to school person, THATS ANXIETY INDUCING. what do i do going forward to help myself?