hi hopefultoday, welcome to PC

Yes, for some people depression can come and go. Mine certainly does. I tend to build up tolerances to medications, so they'll work for a while, then I'll start feeling low and have to up the dose/switch meds. So it may be possible that you need to adjust your medication. The other possibility are external factors like the weather or the things going on in your life. Has anything significant happened in the last little while that has upset you? For me it can be anything from a change in the weather (I tend to get worse in the winter or if it's been really rainy/miserable for days on end) to added stress at work, an argument I had with a family member, or being told something hurtful by somebody else. Have you talked to your therapist about your dip in mood? He/she might be able to help you figure out why you've been feeling this way.

Please keep us updated on how you're doing. I hope you feel better. Best of luck.