Thanks for sharing your experience w/ supplementation. It's definitely tricky to navigate the world of vitamins and supplements. I'm convinced that some of them actually do work and work well while others certainly are a complete waste of money.
It's my opinion that you should consider doing a bit more research on the multivitamin. What brand are you using? Most inexpensive brands, like Centrum Senior and the like, are made of low quality, non-bioavailable ingredients (i.e., your body won't use 'em) and are usually at the top of the "total waste of money" list. I used to take a multivitamin in hopes that it would "fill in the gaps" in my diet but have since opted to get most vitamins through better diet and only supplement those that are hard to get through food, like D3.
Labdoor is a good place to start when evaluating supplements, although one could argue even their site has some bias as they do sell supplements:
https://labdoor.com/rankings/multivitamins