Third trimester exercising

So I'm newly in my third trimester and I have had a few physical set backs and had the first trimester blahs, so my exercise routine hasn't been regular through my pregnancy. I was doing a 60 min cardio scuplt & strength training combo previously.
My question is: I am fatiguing very quickly, like after 30 min. I was able to do 60, then down to 45 and now it seems like 30 is all I can do withould being exhausted for the rest of the day. Is this normal for the third trimester? 
I am willing to go slow, but I still want to tone up. Any comments would be helpful. 
Thank you!