Do I have the right to be mad

Okay so two days ago I asked my sons father for some money so I could buy our son some summer clothes and shoes because he has none. He claimed that he had absolutely no money and couldn't help me out until he got a job (the same excuse he's been using for months) well I just found out that he's at the beach with his new girlfriend and all of her family and honestly I'm kind of pissed, he doesn't have the money to get his child clothes but has the money to go on a beach trip (before anybody says anything the gf couldn't pay for him anyways because she's only 15 and her family wouldn't pay for him so I know he had to pay for his share of the trip.) somebody told me I shouldn't be angry over it but it ticks me off because he never does anything for our child at all and usually I don't even bother asking for his help but this time I really needed him to help out some. Our son is two and his dad has literally only bought him at most five pieces of clothing his whole life. But apparently I have no right to be angry over this. 
(Btw we are teenagers.) And I wouldn't be mad about it at all if he'd actually help out with his son, it just pisses me off that he has no money to spend on his child, but he has the money to go on beach trips, buy his girlfriend things, and constantly go out to eat and get fast food.