Zoloft not working?

I just wanted to throw this out there to ask a question—but recently I’ve been struggling with my Zoloft. I’ve been taking it since I was 12 (I am 19 now) and I’ve been on 100mg for the last year. I was comfortable at 75 for a long while, but just after a year of 100 it feels like it’s not working anymore. Is there a specific reason behind this? Currently just frustrated and I don’t really want to move up another dose.