I am an 18 year old gay male, and I'm pretty well-endowed. For the longest time, I have worn extremely uncomfortable underwear that wasn't even close to being big enough. Although, I'm a pretty slim guy, so finding underwear for my physique has never been easy. Large underwear is big enough to fit my dick, but never small enough for my waist. Small underwear, which is what I wear now, is small enough for my waist, but might as well be girls underwear since there is literally zero room for my dick. I've torn through almost every seam in most of my underwear, and I recently brought up the issue to the only other male in my household: my dad. I showed him a few brands and styles of pouch underwear, which comes in small waist sizes, but has plenty of room. I expected him to be open to the idea, but instead, he said he would never let me wear anything so immodest. I even told him that constricting underwear has negative health effects, but he still objected. I thought this was very strange since he's known about my size for a bit of time. In fact, we've already been down this road before. When I was around 15-16, I told him that I needed bigger underwear, and he actually bought me adult underwear for the first time. However, I quickly stretched and ripped the small pouches and once again needed more. The underwear he bought me after that are the pairs that I currently wear, but as a teenager still currently going through puberty, my dick tore right through those as well. In my opinion, when having a big dick, modesty is a bit more difficult when wearing underwear regardless. However, comfort is the issue on the table, not modesty, which I feel is already an issue with my current extremely tight underwear.
I asked him if money was the problem, but he responded by saying that wasn't the case.
He also suggested boxers, but I said that they're very uncomfortable and I would much rather wear supportive underwear. He just walked away from the conversation, and it hasn't been brought up since.
I need some advice on what his problem may be and how I should confront him about it. Is it because of jealousy? Is it because he feels weird talking to his gay son about his penis? All I want is to feel comfortable, and I don't know how to tell him that without him accusing me of being immodest again.