Fear of crowded places or loud noises recently started?

I was signed off work last week with stress after I couldn't stop crying at work. Now, my GP has advised me to get out as much as I can and do things I enjoy. But I have found that I am now getting panicky about being in crowded places and feel sick and dizzy and just overwhelmed. This is new. Even when I went to my doctors surgery, there was a couple of kids running around in the waiting room and the surgery has sqeaky floorboards and the combination of the two left me feeling totally overwhelmed. I feel like I'm cracking up. Its worrying to me as my work place is really busy and noisy and I don't feel like I could cope with it any time soon. I am trying to fight the feelings and make myself stay in places that make me feel panicky and try to ride it out, but it is hard. I don't want to be in a position that I will avoid places because they make me feel panicky. Any suggestions?