is it possible to tone up without reducing calories/dieting.

I’m really wanting to get rid of my belly and muffin top. I don’t really have the option of reducing my calories because I’m still breastfeeding my 16 month old but I will be cutting out sweets and pop. I’m not really looking to lose weight. I’m 5’7 145lbs so I think I’m good there. I’ll add some photos of what I look like now. Please no rude comments! I just started working out about 5 days ago and do 15 minutes a day. My plan is to work up to more but this is currently all I’m able to do because I have never worked out before!