How can I keep my curly hair hydrated?

I'm mixed race so my hair is rather curly and can get really dry. I haven't had my hair fully professionally cut since I was like 3, I don't like hairdressers because my mom used to cut my hair like bald headed when I was little and I got teased in school because of my hair so I don't like anyone handling it. But my aunt who used to be a hairdresser trims it for me. For like 97% of my life my hair has been in a bun but since sometime last year I started to straighten it for special occasions. It used to be just past my shoulders and now it is about an inch above my waist so I think letting my hair free has made it grow more so it actually gets some air. I straighten it like once/twice a week. I'll semi straighten with a hair dryer then go over it with my straightners at around a 50 degree heat but my hair is still dry/frizzy? After I style it it will look fine, but then as the day goes on it gets dry/frizzy (I'm not quite sure which one). I use moroccan argan oil on it all the time, I've recently been using pantene's split serum or something for dry ends and I have a hair mask every sunday. Any suggestions how I can keep my hair hydrated and not frizzy during the day?