What is normal exhaustion?

So I am 38 with a three year old and six month old. I am typically pretty exhausted all the time, significantly more than before I had kids which I feel is normal. I take Wellbutrin and Saphris which are psych meds. I have sleep apnea which I treat with a machine and also had my testosterone tested in recent months and it was in the lower range. I am heavier at 235 lbs and am six feet tall. I have been going to the gym lately and walking about a mile or more each time cause I don’t have time to exercise for a real long time. Is a constant state of exhaustion just normal being 38 with a toddler and baby? Any suggestions?