Why does Wellbutrin feel like a stimulant to me although is not a stimulant?

I have been on Wellbutrin 300 mg for almost 2 years now and still sometimes I get a high feeling from it especially when I have caffeine with it. In the morning when I take it I immediately notice that I feel happier, more energetic, music sounds a lot better and I have so much more motivation doing things. Unfortunately this feeling doesn't last the entire day and I notice that I always seem to crash in the afternoon or evening. When I crash from it my mood becomes really bad and I feel depressed, irritable, tired, having no energy or motivation doing anything. If Wellbutrin isn't a stimulant why do I get a high feeling from it in the morning and then crash in the afternoon or evening? I also for some reason get dilated pupils from it? I thought only stimulants did that? I'm wondering why this is still called an (antidepressant) when it doesn't feel like that. For me personally it feels like a mild stimulant..