Pregnancy 4 months after getting a tubal?

I am a married 24 year old mother of 4.I recently got a tubal done after i had my son in February since then i have had normal periods. No irregular periods or spotting in between.I wanted my tubes cut tied and burned but my doctor would not do it, reason that the clamps were more effective. Well a few days ago i got sick and I have been tired lately and i had some spotting yesterday that stopped. It makes me extremely nervous because that is exactly what happened with my last pregnancy! Has anyone gotten pregnant so soon after having their tubes clamped?