Freaking out

So there is a chance that I may be pregnant and I am so scared. I love the 2 kids I have with all of my heart but the thought of adding another makes me want to jump off of a cliff. Last week we had a bit of an accident and did not use protection, although I tried it was just too late. So here I sit, analyzing every symptom over and over. I am tired, my chest hurts, etc. Of course these symptoms can be attributed to things other than pregnancy but none the less I am scared crapless. Would I love the baby, of course! However I have no desire what so ever to ever EVER EVER be pregnant again.