Should I accept his proposal?

My boyfriend recently proposed to me after a year-and-a-half of us being together, and I didn’t accept because I am not sure how I feel about this. He wasn’t offended by my response, but I know he is hurt. I love him a lot and wish I could accept immediately but I feel as if I need more time to understand if this is the person I want to spend the rest of my life with. At the same time, I am concerned that if I don’t accept and we end this relationship, I may not find someone as compatible as we are together. I am aware that this sense of doubt is probably normal for a lot of people in my situation, but I don’t know if I am being unnecessarily critical of this relationship. Should I accept his proposal and stop overthinking it?
It’s an important decision and deserves as much time as you choose to give it. To accept a relationship just because it is perfectly acceptable sounds fine, but it is also important to be happy with what you choose to do. This isn’t about overthinking as much as it is about wanting to be sure about a lifelong commitment. If you need time, ask for it. If your boyfriend is sure about this, there is no reason why he shouldn’t be prepared to wait until you are ready.

I have been thinking about my ex a lot over the past few weeks and am tempted to reach out to her. At the same time, I am not sure if this is because I genuinely miss her or because I am just lonely and feel like being in a relationship. What should I do?
You don’t have to get into a relationship just because you’re lonely. If you want to meet your ex, there’s no harm in reaching out, but think of why things ended between you two. Also, you’re assuming she feels the same way, which may not be true.