implantation bleeding vs period bleeding

My period was supposed to start Wednesday last week. So it's late by about 4 days. Usually I'm always on time maybe with one or two days difference and I never have spotting. I had yellow discharge instead for those few days. I'm starting to think I'm pregnant but I don't know for sure. Today I started bleeding but it was a light amount of bleeding compared to my regular period bleeding. I'm going to do a pregnancy test next week or when my boyfriend gets back from visiting his family after next week so we can see the results together. But could I please get some insight on how to tell the difference between implantation bleeding and period bleeding. More specifically ok how it looks. Thanks :)