My [43F] kids constantly choose my husband’s [43M] GF [29F] over me and he won’t intervene. How can I get him to back me up?

My husband and I were together for 8 years before having our first son, and things changed drastically after we became parents. My desire level died because of exhaustion, being a new mother, etc. Although he did help a lot, I just never got the same level of desire back, and after the 2nd son we had to have a conversation because it was becoming a major issue. I really didn't care about sex anymore, although I was willing to go along with it, there were some lines I drew that I hadn't before.

He came out as a furry a year into our relationship and I went along with it, but after children I decided that it made us incompatible and I didn't want to partake in it anymore, and I suggested if he wanted more sex and someone who was willing to pretend to be various animal characters, he get a GF.

He found one after about a year online, and although I did initially suggest it, I wasn't happy. I didn't believe that he could find someone because he is ADHD and might be slightly autistic. She is very eccentric and according to her parents, she is diagnosed autistic, but she is a very sweet woman and gets along with everyone.

After a while I agreed that she could move in with us and things were going well, but over the last two years there have been a lot of issues that I don't like:

Husband spends more time with her than with me, and they send eachother cutesy texts, which he never does with me Her parents are well off and buy my kids expensive gifts that make my parents (and to a lesser extent his parents), their real grandparents, look bad) The kids seem to like her more than me sometimes, for example she spends a lot of time teaching them how to draw, which especially our oldest son loves She wears animal accessories in public

Last week we had a snapping point where we went out for lunch after picking up the kids for school, and I suggested we go to get haircuts for the kids and then go to the speciality cheese shop that is in the mall where the hairdressers are.

My husband wanted to go to the comic book store instead, and GF agreed as she wanted to get a bobble head. I asked the kids directly if they would rather go with me or GF, and they both chose GF.

It just seems as if I am falling out of favour with my husband and kids, and I want advice on how to reverse this. Since we are married, I expect my husband to back me up on issues like this, how can I make that happen?

TL;DR: My husband and kids prefer his GF to me, and I am getting upset and want to know how to get him to back me up