Im soooooo stressed please help!!!!?

So I'm a junior in high school. I've always been pressured by my parents to get good grades in school, but I get like unbearable amounts of homework. I feel like none of my friends are getting as much homework as me and I'm always just swamped. Also I'm an advanced art student and I have a show going up in june and its a show of portraits, and I have one month to finish the last three which is going to take up sooo much time because they're oil paintings and my style is photo realism. But I never have time to work on my paintings because I'm always doing homework. I'm also on the swim team so I swim about two hours each day. And on top of all of that, I have adhd so its hard for me to focus on anything for a while...but that's why I swim cause it helps dampen that a bit...but I just feel like I have so much going on that my head is going to explode from the pressure!!! Is there any way to help calm myself down and do something to make my workload seem more manageable and realistic? Please anything will help!!!