How to give suggestion to a man?

my boyfriend has been saving up for years and last month he decided to buy a small house. Although some renovations have to be done, but he's happy with the decision he made. Until the last 2 weeks, he complained about the tree in front of his house, the noise from pet shop nearby and then he start thinking that maybe he bought the wrong house, or he bought it overprice because there are a lot of things needs to be done with the house. Lately, he gets easily upset. He thinks hard about how things should be done, and he even got sick. I tried to support him, in whatever his job/his plan, tried to listen to any of his complaints, but sometimes i get confuse of how i should react without make him feel like i am preaching. I just want to comfort him, but i don't know exactly what to do or say? please help, thank you :)