My daughter will not sleep! Help suggestions please!

I'm desperate. My daughter will not sleep! I'm lucky I can get her to nap 45 minutes the whole day. As night time approaches shes usually so exhausted and a complete mess but she just refuses to lay down or sleep. If I try to put her in her crib she just yells and beats her head off the crib. If I lay her in bed next to me, she just rolls around like crazy non-stop... I make sure she eats good all day. Ive tried everything. Rocking her, music and lullabies, warming up her bottles, cereal, warm baths, etc. I just don't know what's wrong??? I'm so exhausted, I don't know what else to do. I'm also 18 weeks pregnant so this stress is just killing me. Any suggestions please???