Do I need Plan B?

Throwaway because my ex knows my usual account. Yesterday was my birthday so I got drunk pretty early in the day, drunk enough to forget to take my birth control pill. I thought I had taken it so I didn't realize I actually didn't until I was cleaning up after last night and found my BC pack. It had been about 20 hours since I was supposed to take it. I just went back on Tricyclen-lo about three weeks ago, in fact I just took the last (not placebo) pill of my first pack today along with the one I forgot yesterday. My period ended ~2 weeks ago.

I have a FWB so of course he came home with me and we had birthday sex. Once last night and once this morning. He can only ever cum when he's drunk from me blowing him so he pulled out well before he finished because it took awhile after we switched to 69ing. This morning he pulled out and came on my back, there was about a five second gap from when he pulled out to when I felt it hit my back. He peed this morning before we got frisky.

Usually I would go and get plan B without even thinking about it but I'm SO strapped for cash right now and it costs ~$40 at the only pharmacy open on Sundays. I know a baby would cost much more but if plan B would be excessive I'd like to avoid having to get it. He went out of town today so I can't ask him to pitch in to help, plus it was my stupid fuck-up so I'd hate to ask.

Am I being stupid? Should I just suck it up and get plan B or should I not worry about it? I just turned 20 and all the jokes my friends made last night about me escaping teen pregnancy are just making me cringe now.