Need Help With My Preschooler

Is it normal for a preschooler (3 1/2 year old boy) to regress and go back to pointing and grunting instead of  speaking, NOt using the potty ever-even though he was potty trained before, refusing to feed himself, agression, howling for absolutely no reason at all, (the lest can keep going)? Im at my wits end not knowing what to do.
I have 2 older daughters ages 23 and 22 years old(!) and there have been no recent major changes. He just started regressing about 6 months ago. I am not sure what to do or where to turn at this point.

[margypops]

not unless he recently had a baby sibling he feels jealous about ?

[margypops]

I would get him evaluated by the doctor what is going on .