Should I get the IUD

I’m scheduled to have the Mirena IUD inserted in just over a week. I am 8 weeks pp. at first I was super excited about it but now I’m having second thoughts. At the moment I am not getting my period since I’m breast feeding so having it help with periods is pointless right now. I honestly don’t mind sex with a condom, it’s what me and my husband did before trying to conceive and it worked just fine. I’d like to have more kids eventually. Once my newest is at least 3 and we’ve moved into a bigger house so I don’t want the IUD ruining those chances. I’m also trying hard to lose weight and I’ve heard the Mirena IUD can cause weight gain. I’m not sure if I want it anymore. I’ve already had my consult, bought the device, and booked my insertion but I’m thinking of cancelling. Anybody have any stories they could share good or bad regarding their experience with the IUD.