SSRIs can indeed have sexual side effects like decreased arousal, so you may notice some changes as you continue coming off that medication. Too, you're smack in the middle of puberty right now, which is a time when a lot of people notice changes in their sex drive.
You're also right that if you're not aroused, clitoral stimulation is unlikely to feel good. Our brains are our biggest sexual organ, so if they're not engaged in what's going on, it usually doesn't feel like much (there are also some people who don't enjoy clitoral stimulation when they are turned on, because different bodies enjoy different things).
In terms of how to generate arousal, have you seen this article yet? If not, it's a really good starting place, as it walks you through different things to try: How to Approach Sexual Fantasy and Desire on Your Own Terms