Working out while pregnant

so I'm a stay-at-home mom and I'm 5 weeks pregnant with my third. I like to work out so I can only really work out at home because I'm around a little ones all day I do about 20 minutes maybe more if I can of aerobics I try and do it every day except on the weekends because I'm just too busy. I feel like 20 minutes is not enough but I have been getting really tired very quickly I used to be able to do about 30 to 45 minutes before I found out I was pregnant. I guess my question is is 20 minutes enough of mid intensity aerobics I've been doing workouts that cater to pregnant women so it's not too high intensity.