Been only gaining belly fat during dirty bulk

Hello, I am a 17yr old 5'11 male who has been on a dirty bulk because I have been consistently skinny my entire life. The reason that I am on a dirty bulk instead of a clean one is simply because I still eat whatever mom gets from the grocery store (along with little things I'll buy myself). My goal is to eat 4000+ calories per day and I have not failed with my highest recorded day being 5380. I don't track protein as I already make sure to eat very high protein sources, such as my own mass building shake that I make. I started with a morning weight of 156 lbs, now up to 174, yet the only gains after 2.5 months I've noticed... are in my belly? I'm not even gaining fat anywhere else on my body which is strange to me. However, my strength has upped a decent amount. Prior to bulking, I've been consistently hitting the gym for 10-12 months, and I always make sure to push myself near failure on almost every set. Should I just give it more time to gain real muscle or am I doing something terribly wrong? I've been trying to reach a morning weight of 180 before a cut... Yet the only thing to cut is my belly.