Spotting after sex (very paranoid!)

So my BF and I have been having sex pretty frequently the last few days and I’m noticing like 12-24 hours after we have sex I start to spot a tiny bit. It ranges anywhere from brown to light pink. I’m thinking it’s from irritation or friction because he has a pretty good sized *wink wink* and I’m like 5’2 100lbs, very tiny. I definitely feel like the term ‘being up in someone’s guts’ applies to me.

I also have hormones that are out of whack and I spot randomly sometimes, so I feel like maybe he is just pulling out some old blood or something. I’m 23, in good health, Dr. doesn’t seem too worried but I just wanted some other opinions or stories.

Thanks!