Is my baby getting enough ? Feeling concerned 🙁

My first pregnancy went smoothly and I didn't show a bump until the last 2 months and I had a boy. This time I'm due a girl and Iv put on weight much quicker at the start and had a good appetite but I have been feeling sick since the start , nausea all day ,rubbish sleep , bad back, tummy upsets at least once every 3 weeks and since 18 weeks my appetite has been getting worse and worse . I don't fancy anything and the pregnacare multivitamin tablets make me feel more sick so don't take them . I'm worried my baby won't be getting enough but forcing myself to eat properly makes me I'll and so do the vitamins :-( I'm not doing lots of exercise as I feel ill and my back aches just standing up for 30 mins , so I'm just going for walks when I feel able to . How do I know if my baby is getting enough?

I didn't have any of these issues in my last pregnancy and I'm now 24 weeks and feel like my bump isn't progressing like it did at the start when I still had my appetite.

Any advice please ??