(Long post) Can Sertraline side-effects return after coming off?

I have post cancer/chemo PTSD, and it generally seems to bite in the summer, June-August months. 

Last year I was so devastated that here it was again (manifests itself in disrupted sleep leading to massive, beyond reason anxiety about the sleep issues) that for the first time I begged the doctor for meds. Her recommendation was Sertraline. 

I felt foul on it, and my mood was very low but in a weird way I wasn't quite so bothered: if it was the meds making me feel so rough, that was better than losing my mind. 

The doctor suggested trying to reduce after 6 months. By that time my mood had come up to normal ~ unsure, of course, whether it was the Sertraline or just its normal progression. 

I tapered very, Very slowly. I bought myself a scalpel, and shaved a bit off one tablet once a week, then twice a week, then a quarter off, then half. I didn't feel any side effects, either physical or mental. Phew, I thought. 

About a month ago, my sleep became more erratic again. I'm trying to lose weight and, ironically, most nights when I was eating like a waste disposal, I slept like a log; when I'm losing weight, it's much more erratic. However, I've worked very hard at trying to keep the mood up, some days are better than others but I don't feel the need for meds. 

One of the big side-effects of Sertraline for me was the teeth-clenching, something I hadn't normally done. That wore off ~ but it's back with a vengeance! So here, eventually, is the question: Can the side effects of Sertraline return like a twitch of a shark's tail, even after you've come off? 

I don't remember exactly but I'd finished taking them by Easter, and I was only on 50mg. 

Thanks.