What changes when you get married?

Po

So me and my boyfriend planned to get married. I was about to buy my wedding dress and I was planning with his mom and were we're getting things ready (I was 4weeks pregnant at this time by the way). Now he wants to hold off getting married... his reasons were

My perfect credit score: he says that his debt (student loans and other loans) will ruin my perfect credit score if we were to get married.

My insurance: i will lose all my current health insurance and so will the kids and he will have to put us all on his insurance which he was proud about when he mention his benefits to me. (I knew this would change tho.)

His taxes: he would have to do another tax form which he doesn't want to do because they will take more out of his check.

Documents: basically he doesn't want to do the paperwork

Im not sure how much of this is actually true... that's y I'm asking I know the insurance is true but I'm not sure if getting married is as complicated as he's making it seem. He doesn't want to do it anymore now.

Update.... we already have a house and cars. I have two children from a previous relationship (he loves them by the way they love him. The father is barely involved.)