Frog having trouble eating

[Vinegar]

I've had my pacman since March, and throughout the year he's been eating and passing just fine. However, over the past couple months I've noticed him not eating as ferocious as he used to. I've had him since he was a wee froglet, and at the time I fed him only small dusted crickets daily. He's about three inches now and I've been feeding him 3 dusted superworms every other day for maybe 5 months with some variation in the feeding schedule and amount. He has had trouble with passing stool before but I've taken care of it each time and he is a pretty healthy frog from what he lets on. Anyways, often when I feed him nowadays, he just opens his mouth and sits there waiting for me to put the food into his mouth. Other times he just isn't in the mood to eat. That would be fine but he doesn't bite down very hard and it looks like he struggles when he eats. I switched back to crickets today and when I fed him one he struggled greatly to eat it and just acted lethargic like he really wasn't hungry and that he was just eating so I could leave him alone again. Outside of eating, he's kind of an active frog. He isn't lethargic in motion or crawling or even hopping, but when he eats he just loses that energy. Could I be over feeding him? I'm not sure what to do and it would be greatly appreciated if someone could help.