do I need to take a pregnancy test?

So I’m on birth control and last week i did a pretty horrible job of taking it. One day I took it 6 hours late, the next day 12 hours late, the next day I missed and the day after that I took them both at the same time. That night my boyfriend and I had a little too much to drink and I let him finish inside me twice. We decided to buy plan B and so the next day, he came inside me again because we were going to buy plan B. A lot of unexpected things occurred and now it’s 4 days later and I have yet to take plan B. Yesterday I had brown discharge and light cramps which I didn’t think much of, but I never have spotting so today I looked it up and it said it could be implantation bleeding. Is this something i should be stressed out about? I know it’s way too early for a pregnancy test but should I take one anyways? I plan on buying the plan B today, i know the effectiveness is less after four days but it is still worth it.