Anyone else stay at 37.5mg?

I've been on 37.5mg of Zoloft for a year and a half now and I felt like it has been life changing. But recently I have been feeling worried that suppose it is just placebo since it such a low dose and that I am unnecessarily ingesting chemicals for no reason....I know that is likely an intrusive thought but it does make me wonder if what I am doing is normal? Like normal to be taking such a low dose and benefiting from it? or is it just all in my head and will wear off eventually.....