GP dismissed my assessment referral request because I'm "hormonal" - what can I do?

Hello, and apologies if I'm breaking any rules by not posting an introduction in the relevant section first.

For over a decade I have suspected that I'm autistic after reading about autism by chance, and having been told by work colleagues, some who had experience working with autistic children, that they thought I might be autistic. As an adult, I managed to adjust everything in my life to accommodate my needs: get a job which I can do from home, only communicating with my clients via a couple emails per day; limit social interactions to a small group of people sharing one of my special interests; having perfect control over my indoor environment and daily schedule to eliminate anything that might trigger my sensory issues. It was working very well for me and I felt no need to seek any help.

Everything changed since I've had a child, as suddenly I was not able to follow my routines, plan my day, have sufficient time to be alone or to pursue my interests, have space in the house that would be just mine, or get a break from physical contact. Parenthood also comes with many more social interactions which I am not able to successfully perform. This, and the fact that I have another child on the way, made me decide it was time to seek professional advice to navigate the issues I am facing.

I made an appointment with a GP. It was suddenly rescheduled yesterday, from mid-April to today. The sudden change, and the fact it was to be a telephone call, made me very anxious, but I made a list of things to say and was methodically going through them when talking to the GP. Yet he cut me off before I got to the end and said that he would refer me to an antenatal clinic for my anxiety and depression which were due to me "being hormonal", and that even if he referred me for autism assessment, they would not be able to assess me anyway due to my being pregnant. I do not understand why this would be the case, and neither am I suffering from depression, being by nature optimistic and deriving great joy and sense of fulfilment from my special interests. I explained twice that I suffer meltdowns from being unable to follow my routines, from sensory overstimulation, and a feeling of lack of control because I cannot plan out my days. No matter what I was talking about, he kept saying it was because of pregnancy hormones.

I do not know what I can do now. Will the GP practice people be angry with me if I ask to speak with a different GP? Can I make a complaint, and to whom? Or should I go to the antenatal clinic so that the therapists there can see that my issues are not relevant to their area of expertise, and they would then refer me for an autism assessment? I will be very grateful if anyone can offer advice on what steps I should take.