Hello! Congratulations on your pregnancy! I do apologise for the delayed response ! I was away on holiday .
If you have been exercising prior to your pregnancy,then there is really no concern about when to stop .
You can maintain your programme with cardio and weights for as long as you can .
The tiredness could be the hormonal changes in your body , but exercising will counteract that !
Keep going !
Be cautious of running and exercising on your back.