Exercise while pregnant?

I am 6 weeks and 3 days pregnant.. is it okay to do light exercise? I have a thing like the air-walker thing kinda like the gazelle freestyle but not that its all manually powered and the restraint weight is ur own body. so with it its like ur walking its not a belt one like a treadmill... is it okay to still use it? i only walk on it like 30 Min's maybe an hour a day.. also what exercieses are good to do when pregnant