I think I may be pregnant

Last month I didn’t get my period like I usually do. It was really late, and then not even a period at all. I just spotted for a couple hours for like 2 days. Then a few days went by and the same thing happened. I heard that may be “implantation bleeding”? I’ve been super moody and starving like all the time. My boobs have been tender and my back is really achey. I don’t think I could be very far along, if I am, so idk if I’d even be experiencing anything. I’m scared I’m just over thinking everything. I’ve taken two pregnancy tests. The first said “invalid” and the second one(I took it about a week later) said it was negative. Sooo, ya girl needs some help, please?💛💛