Nemmie has given you some great advice there I would definatly listen to what she's said
You shouldn't be doing more excercise than your body is used to, and don't over streach or lift anything heavy during your excercise. I think the general advice is that this early on you only need an additional 300 calories on top of the recommended daily amount for a woman - however your body may ask for more. Keep rehydrated - as you will need more liquids now.
It's good that you're keeping fit, don't forget at the end of all this your body has to go through the most grudeling physical it will ever encounter, there is evidence that women who remain active during pregnancy find labour easier.
And do not over do it. If you feel lightheaded, dizzy or faint stop immediately

Remember, at the end of the day it is not worth the health of your baby.
And congratulations btw
