FTM feeling guilty for wanting to do things for myself

I’m a stay at home, FTM of an almost 7 month old. I love being a mother and I love my baby more than anything. But lately I feel guilty for wanting to invest in myself. Not materialistically but in terms of trying to feel like me again. I got my hair done last week which was much needed and it gave me a boost of confidence. I’ve been adjusting my diet and eating more healthy and even recently got back into the gym. I have this strong desire to get my body back to where it was and I just want to look good and feel good again. But then there’s this voice in the back of my head telling me I should be giving all that energy and focus to my baby. Almost as if I should feel ashamed for giving extra focus to myself. Why do I feel like this? And why am I all of a sudden having a difficult time letting go of who I was before becoming a mother? I miss who I was but of course I’m still grateful for my life now. I don’t know how to find a balance between being a mom and being my own person too. I have a fear of losing myself but want to give my son everything I can possibly offer. Does anyone else feel this way? Please tell me I’m not alone