<human>: Can you summarize the given text in a few sentences?

We've been together for 4 years, living together for 3, no major problems at all, and we rarely argue. We are very comfortable with each other since even though we've been dating for 4 years we have known each other since high school. We do have very different personalities, I'm outgoing, social, adventurous, he's introverted, extremely private, and definitely not adventurous. However, I have lots of friends that I do my adventurous activities with (rock climbing, roller coasters, travel, etc). Financially we are very intertwined since we've been living together for so long.

He popped the question a couple months ago, and I said yes. It was a surprise to me, and I did have a millisecond of hesitation in my head, but it passed quickly and I was excited and happy to be engaged. 

Now, a couple months later, I've found that when I see movies or shows about marriage I get nervous, and I find myself wondering if this relationship is really the one I'm supposed to be in forever. However, I've never been someone who focuses on marriage and kids (we don't plan on having kids), so maybe the nerves I'm having are normal. So that's my question, is it normal for me to be having these fears/doubts or is this my inner self trying to tell me not to get married.
<bot>: Recently engaged to someone with a very different personality than mine after 4 years together, having lots of nerves and feeling some doubts about getting married. Is this a normal reaction?