Can weight problems give you complication on trying to become pregnant

I struggle with my weight constantly going up and down all my life my fiancé and I have tried last year to have a baby and which I got a positive pregnancy test but after 2 month I  had a misscarriage and ever since then my weight has been skyrocketing up and down and been getting negative test for a while now :( I don't know what to do if anyone can give me some advice would gladly appreciate