Supplements.. etc

I have three kids from a previous marriage so I know it's not me...

my husband now is younger than me.. he's 24.. he's in great shape and super healthy... we've been trying for a year..

I got pregnant with my other three like within a month... I had Mirena IUD for two years before me and my husband now started trying.

Ive got him taking vitamin C vitamin D Zinc and ashwanganda.. hoping it helps. He also takes testo boot a testosterone supplement which I think may be hurting our chances of conceiving. He said he'll stop taking it.. Any other tips?? We BD every day or every other day through the entire month.... my periods are regular..