16M Old lost some words while learning new and stopped calling mama for a month, regression concern?

[saitnyc]

Hi everyone,
first time parent here, healthy 15M Old boy, met all milestones for 18M, except for speech which concerns me due to my anxiety.

He started saying his first words mama and dada at 7-8 months. After 13 months he started adding few more so at 15 Months he knew 5-6 words beside mama/dada and he imitated 7-8 animals.

Hovewer, while working with him on some new words, past days I noticed he learned anjanja for banana and deer, but I also noticed he forgot to imitate snake (ksss), and forgot to say njam njam when hungry (instead he will just finger point to plate and say mm ).
We also noticed that he stopped calling us mama/dada for over a month.
When you ask him where is mama he will easily point/look at mama, but will not say mama.

I read a lot about regressions and internet articles can be concerning, but I really need advice for experienced parents is behavior like this normal, or we should react and seek for professional advice?

Maybe we are too anxious about development and not sure is it smart to push him every day with checking on his words knowledge, or we should be more spontaneous....
Thanks

My daughter did this. She only ever had 3 words if she learnt a new one she lost and old one. Our HV did an assessment she was 20 months at the time and she ok on the 12-18 month assessment but scored 0 on the 18-24 month assessment. We were given some exercises to do. Lots of enforcing language. By 2 she was up to 10 words but most communicated with pointing she started a new nursery and in 2 months she came on loads and when she had her 2 year assessment at 26 months she did ok. By 3 she was on par with my friends kids who were so far ahead of her at 2!
She's August born and at 2 we thought we would have to defer her school entry but she's just finished her first half term at 4 and 2 months. No concerns with speech and she's picking up phonics really well.

She had a hearing test at 7 months due to a delay in responding to sounds but she passed that. If she hadn't she would have been sent for a hearing test.

It would be worth messaging your HV to get a speech and language assessment, get done advice on keeping words and maybe a hearing test and go from there