I just wrote a response and submitted but it is missing 🙁 Also, I noticed I wrote boyfriend when I meant husband, so sorry for that!

You can be very confident, intelligent, social, etc. in life but still be very insecure in relationships (either fearful and anxious or avoidant and repressed), unfortunately.

Here are some quotes from the book to describe more of what I think your husband is going through:

“If you’re anxious, when you start to feel something is bothering you in a relationship, you tend to quickly get flooded with negative emotions and think in extremes. Unlike your secure counterpart, you don’t expect your partner to respond positively but anticipate the opposite. You perceive the relationship as something fragile and unstable that can collapse at any moment. These thoughts and assumptions make it hard for you to express your needs effectively.”

“When your partner feels s/he has a secure base to fall back on (and doesn’t feel the need to work hard to get close), and when you don’t feel the need to distance yourself, you’ll both be better able to look outward and do your own thing.”

One suggestion I will make for your current predicament:
Try gently suggesting that while you spend time with friends or do something on your own that he do something simultaneously with friends. If he doesn’t yet have friends, encourage him to find a hobby or activity meet up where he can meet others and form other close relationships. At first it will at least help distract him from the distress he may feel when he thinks you don’t want to be with him. And then afterwards, make plans to meet up for a dinner, a date, something more intimate, to share your experiences. It’s a way to positively reward his venturing out to do his own thing knowing you’re at home waiting for him while also giving you that healthy breathing room you need.

When I was insecure about my boyfriend making all of these plans for week nights and not making time for me, he suggested that after I get back from one of my hobbies that we get together because I wouldn’t see him the next night like he knew I wanted. Of course, this time together must be quality time or else the triggered attachment system (she doesn’t want to be with me and is just doing this to shut me up!) doesn’t truly get pacified…. which must be hard to do if your attachment system is also still triggered (I haven’t gotten the space I need yet!)

Over a year in this relationship I got much better with my attachment insecurity. It was still there, but I got the healthy push I needed to form close relationships with others, which took some time and is an ongoing pursuit. No one person can serve all your social and connective needs.

It seems to me that your husband is very thirsty for reassurance, and if he feels like what he does get is tiny sips, he will go back to being thirsty almost immediately. What could possibly be happening is not that he truly needs to be with you 100% of the time, but that the time he does have with you is not quenching this thirst. I would try to get to the bottom of why and what this is.