A strong relationship isn’t likely to be destroyed by lack of sleep, but being sleep deprived and grumpy isn’t likely to do it any favours either. If you’re both suffering sleep deprivation now that your baby has arrived, you’re more likely to snap at each other about trivial matters, and you’re less likely to be open to communication and compromise.
The good news is that there are several ways you can get more sleep, and that should solve any problems you may be having. One good idea is to arrange with a trusted friend or family member that they stay at your home for a night or two, and you and your partner head to a hotel. Being out of the house completely should give you both the time the rest and recharge that you need, and when you return home, you’ll both be fresh and ready to face the demands of a new baby again. Alternatively, you could have someone stay over while you’re at home, to allow you and your partner to sleep and relax, but still be around to breastfeed, and if your baby really needs you.
Once you’ve both got enough sleep to communicate calmly and rationally, sit down together and come up with long term sleep strategies that will leave you both feeling less exhausted. Alternating with baby care responsibilities, dividing up chores and lightening your workloads are all options that can work. Alternatively, you might decide to hire temporary help around the house, or with the baby.