My son is getting slim & not eating food

I have a baby boy of 15months old & I am a divorced father nowadays as he is growing up he is active but sometimes he skip his meals as well & even sometime his mood also gets at a frustrate level like he makes irritate by crying or he gets self confused like he want something to play but he is not sured actually what he wants & mostly he do these things at that time when he feels sleepy help me out for feeding him,increasing his weight & keeping him in a good mood all time no doubt in we all give him lots of love kindly help me with above & as from his childhood he has spent like 95% of time with me only so I don't think he is doing all because of his mother cause she haven't given him much time from the time when he was born