I’m not one for giving advice, especially because I don’t know you or your situation, but it sounds like this is something that is really giving you agmas nefesh, and there’s no reason to push off improving your quality of life. (Even if it’ll be easier in EY, why make this a focal point of your sem year?) I don’t think I need to tell you this though ;), especially based on your last sentence which sounds like you really want to be proactive….
About who to tell…
If you asked me personally, I’d vote for teacher, but that’s just because I don’t like keeping things so close and I usually prefer involving as few people as possible. I don’t know you. However, if you discuss it with a teacher (not necessarily your actual issues, but just the issue of wanting therapy) you feel you could trust and would be mature about it, and would have the ability/resources to help you, that could be a great option because it would give you an additional bonus as an adult mentor who is sometimes just nice to bounce things off of. I’m sure there are other bonuses that you could think of as well….
As for a friend’s mother, if you have such a relationship with her and feel that she would do a good job of explaining, especially if she knows your mother and her personality well, I see how that could be a great option as well. Again, I’m sure you can think of other reasons that I wouldn’t know….
I wish I could give you a definitive answer either way. I think it’s really awesome that you’re trying to figure things out, and I give you a lot of credit – it takes a lot of strength!
Hatzlacha!