First pregnancy and spotting

I am currently 4 weeks pregnant (if you go my my LMP, but I ovulated early and by ovulation date I am 4 weeks 5 days). I found out on January 31st which was one day after my period was due. I have been having very very light pink/brown spotting that has been very light. Almost like regular CM but just very lightly colored. Today around dinner time I went to the bathroom and when I wiped there was a decent amount of red/brown. It was almost like old period blood, something I’d get at the end of a period. I went to the bathroom shortly after and it happened again. I haven’t had any since then-back to the light pink/brown stuff that I was having. I’ve been having light cramps since then but nothing like period cramps. My lines have been really dark so far and getting darker. I plan on testing again in the morning. I’m so nervous I’m going to miscarry! Has anyone had any similar experiences?