For me in this situation, long term I would probably regret the fertility side of things rather than the breastfeeding side. When I am old and my kids are adults, the impact of how long they breastfed will be less than the impact of if I didn't have one of them at all.
I was actually convinced that that was how I would feel too, but it didn't take me very long to regret giving up BFing. I think for me, it's because I didn't go on to have another child, and likely won't. It's a lot of pressue to put on yourself to ensure you get pg again, if you're worrying about what you've sacrificed to get there.

I'm sure the right decision will come to you, hun. Just don't rush into it.