Confused about this pregnancy!

Okay so i am 17 weeks pregnant, i had my last child 9 years ago, for a very long time i thought i was not able to have babys anymore, no birth control for about 6 years or more, it never happened, so now i am pregnant again, not planned not expected. Yes i knew it was always a possibility but just with the years i got used to not thinking about another baby, well after all that info my question is, today me and my husband went to the store and he took me over to the baby stuff and started showing me baby stuff we could start buying, well i started to feel really overwhelmed and started crying telling him over and over again that i am just not ready for all this, yes it sounds ridiculous but thats how i feel, has anybody felt this way or is their just something wrong with me? I feel terrible because my husband was so excited to get something for the baby but felt bad for making me cry. But i dont even know why i feel this way.. help please!