Possibly. Pajamas and underwear are not condoms!!! If he released any semen, sperm could travel through his fluid and then through your fluid and then one to an egg. We're talking about microscopic cells that are darn good swimmers. There may be a low probability of you getting pregnant this way, but it's not impossible, and you wouldn't be the first to get pregnant that way.
Again, pajamas and underwear are not condoms. If you're gonna play with fire, get a fire extinguisher... or better yet, leave the matches alone until you can handle getting burned...