I recently did a trade for photos photoshoot with a photographer I met off a model website. I am a semi-new model. There was no exchange of cash only pictures. After the shoot he sent me a model release form via email. I do not agree to terms and am not going to sign it. What happens if I refuse to sign it? Can I still use the pictures for my portfolio on the model website?

This is a classic situation that underscores the need to have written agreements. Of course you never need one until a dispute arises, but once a dispute arises, there is no substitute. Here you have a situation where each party's rights are unclear. Did you get a license to use the pictures on your website? Did the photographer get the right to use your likeness for any purposes? No one knows for sure, and if you use them and the judge disagrees with you, you could be infringing his copyright in his photographs. Get a written agreement next time BEFORE the photoshoot.