Side Effects of Nexplanon?

So, I noticed this week that I haven't had an appetite at all. I get up between 5:15 am and 5:45am to go to the gym. I was super tired on Monday so I didn't go. After the gym on Tuesday I felt super nauseous. Since then I haven't been hungry or had an appetite at all. Today I ate a slice of pizza because I didn't want to go the whole day without eating something. I've been on Nexplanon for about a month now. About 10 days ago my boyfriend and I had sex and he came a lot inside of me. I cleaned up right away, so I don't think that I'm pregnant but I've felt very weird. I slept most of the day today and anytime I got up I was dizzy/weak. I noticed today that I had a brownish color discharge when I wipe. Almost like old period, if that makes sense? Any thoughts??