Bipolar S/O

Ugh so my husband of 6 months (S/O of over three years) is acting so out of character. One minute he's very attentive the next he's acting like I just insulted his ancestors then 10 minutes later he's back to being fine. He has started buying me things (which I'm not compaining about but it's just crazy out of character) he's throwing himself into restorations on his truck all of the sudden but anytime I question something just trying to show an interest in his likes he acts like I'm saying he doesn't need to be working on his truck. I don't know if the stress of TTC for the past two years is getting to him or what it's just getting in my nerves and everytime I try to talk to him he sees it as a personal attack. Why? Why are men so complicated?!