Any idea of what I can do that is not obviously gay (cause parents) but still is sort of supporting pride month?
If your school has a gsa maybe you could see if there's anything you could help out with/contribute during school. Wearing rainbow things If you think it would be a safe idea and you have a Facebook, you could post something about the month or awareness or maybe find a site you could post a link to with information about the LGBT community Hope this helps! But like SpaceOddity said, just being yourself is great. Even if you can't do anything big this year, that's okay. Just showing those around you that you are an accepting person can help people more than you know.
I wouldn't recommend any kind of pins or stickers if you want to be subtle. Unless if you just put on clothes with that color scheme, then it would be subtle.
Here's my idea for you. Find something you can do, or something that you can volunteer for, to aid the cause of youth suicide prevention. This applies to all youth, but gay youth attempt suicide in greater-than-average numbers. Not only will you be advancing the cause of "pride," you'll actually be doing something that is far more than symbolic at the same time.