Anyone tandem breastfeeding ?

I had my little one almost 3 weeks ago and My little toddler is going through a phase we’re all he wants to have is breast milk I’m worried he will not feel good or something because well he supposed to be eating solid as well he was but Iits been like a month he hardly ever eats anything other than maybe cheese sticks or very minimal snacks I’ve tried keeping away even snacks but he will literally go day without eating other than milk so I feel bad any advice? Or have you gone through same how long will this last on side note he is doing perfectly fine good weight n growing I’m just worried