1999 Plymouth Neon

1999 Plymouth Neon- During our hot weather I was using my a/c, but it would bog the engine down to the point of when I pushed down on the gas the car wouldn't go. I had stopped using the a/c and just used the windows, I recently noiced the car would do the same thing as soon as I would step on the gas, without using the a/c. I just had my emissions done today to renew the car, I passed just fine. It was extremely hot today so on the way to get my 4 year old, I ran the a/c to cool off the car for him, it's about a 10 minute ride, no problems. As we left the daycare I turned the a/c off in order to get out into traffic quickly on a busy road. I pulled out and the car would barely go, had to pull to the side of the road in order to not get hit by the fast on-coming traffic. I finally was able to go again, got up to speed and then noticed the check engine light had come on, and when I would come to a stop and try to go again, the car would hesitate even though I had the gas pushed down. What could be wrong? Please Help!