S/o stressed?

So I got my Bc taken out in january and have been ttc since but recently my SO says that sex isnt the same anymore, In his head we are just having sex to make a baby (mind you we've only been actually trying with opk's for this month... And he bought them for me) i feel like he is completely stressed out from it...but he says he is totally on board with TTC but is now saying this to me and its making me think he doesnt want another child(we have 3, 2 are bio mine and 1 is his, but they are all considered ours we are a family) we've been together on and off for 9 yrs and now recently moved in together for the past 2 yrs. Any input would be helpful. PLEASE NO NEG COMMENTS