I've read that if you have greenish discharge you should see a doctor straight away, is it that serious?

Last night DP and I dtd for the first time in like...3 months? It hurt and was uncomfortable and it kinda felt like burning/stinging down there for a while after. Anyway, this morning when I went to the toilet and I wiped there was this gross green snotty discharge on the paper (sorry tmi), quite a lot and it's made me really worried - I was thinking of even keeping it and showing the doctor I've been getting some discharge recently, but not like this. All I can say is, I'm never dtd while pregnant again!!

Any idea what it could mean and if it's normal or really serious?