My partner (29F) wants another child with me (29M) but I feel trapped.

Hi all, I’m in a bit of a predicament so am hoping someone can shed some light on my situation. Context: I’m (29M) in a long term relationship with my partner (29F) and we have a 3 year old boy together. He wasn’t planned and the first year or so or our relationship was very rocky but we’ve come to a place of relative stability and have a strong village around us of family and friends. I love him to pieces and we have a great family bond. The problem is my partner now wants another child. We agreed this year we’d start trying but we’re not in a place financially where it makes sense (we still rent for one) and I also feel pressured into the whole thing. We also argue quite regularly and am generally worried about the stability of our relationship. I know she has a body clock which must be stressful for her but I also know how much work and financial stress comes with having a new born child, especially as my partner won’t be working for 9 months and I’ll be covering the majority of the bills. I still feel we’re so young to be rushing into having another child but for my partner it would be make or break for our relationship if I won’t have more and I don’t want to destroy our family. For me personally, I sometimes get depressed thinking about the lack of autonomy I have in my life when I see my friends travelling and doing anything they want and I know it will only get worse by having another new child with more nursery bills to think about and more sleepless nights. But at the same time, I don’t want my son to be an only child and if it’s a dealbreaker for my partner I don’t want to destroy my family and end up spending less time with my son if we were to separate. I also love my partner who is also a fantastic mum and would be heartbroken if we separated and my life would become a lot harder with working out childcare, no more help from her parents and we’d need to rethink our living situation for our son. All of this I know is a selfish way of thinking but in all honesty I’m not truly happy committing myself to having more children and feel trapped/pressured into doing so. Thoughts ?