HELP 😭😭

My baby girl is 15 weeks old. Shes my first and sim strugling with her every so often shes breastfeed, doesnt have a dummy/pacifier and wont take Expressed milk from a bottle. I feel like shes on me 24/7 shes barely sleeping and constantly wakes up and I don't know what else to do, she uses my boob for comfort and wont sleep without me and I dont know what to do anymore I've literally tried everything. What do I do??