A little advice please?

I need help, my baby is three months old and hasn't been doing well, she screams like she's in pain it's gotten worse the past few weeks but she's always just screamed when she was a newborn to, most of the time she doesn't take naps and wants boob all the time even when I know she's full. I'm a single mom and the doctor said it's all normal and should stop when she's 4 months old, but it's getting worse I don't think it's normal and I feel so bad. She's just always crying but she's a really happy baby she is always trying to smile but she just screams and arches her back, her legs are straightened all the time and always wants to be held. I'm thinking about going to another doctor cause her doctor said it's normal but I really don't think it is. My sister thinks she has collic, I'm hoping for advice or anything I can do for her? I give her gripe water and it can be a 50/50 with helping her. Momma's please let me know if there's anything I can do