Chances of pregnancy?

I'm feeling a little bit idiotic because me and my boyfriend of over 2 years have always used condoms when taking part in intercourse, however they have become extremely uncomfortable and inconvenient (naive I know) so we decided to try another form of pregnancy prevention. Plan B pills seemed awfully expensive and I can't take birth control because I am on other medication that could possibly negatively react to another medication such as birth control and I'm not prepared to take that risk. So we decided to try spermicide. Now last night we used it as instructed and 40 minutes or so into intercourse he ejaculated inside me then pulled out and finished outside of me. Now we've always been very cautious and this is the first time we've been a bit nervous on whether or not we did a successful job at preventing conception. I know I could definitely do it if I happened to conceive but I'm just not sure if I'm ready. Please give me some feedback?