HELP! My baby won't nap!

It's driving me insane becuase she gets super cranky and I'm exhausted! She's about to be 4 months, she's always been a sleep fighter (even tho ppl say she's too young) but she will go until she her eyes are red and she will be dropping and soon as they close for more than 3 seconds she's like boom wide awake! Although she seems to kind of fight her sleep from early on she had always been a pretty good sleeper and consistent but for the past 3 weeks she's been getting progressively worse. It takes FOREVER to get her to sleep! Iv tried everything - making sure she's not over tired, going for walks, car, swing, in my arms, nursing, nap time routine, etc etc! I try and keep her busy in between naps to tire her out! When she does finally fall asleep it's for no more than 20 minutes. Right now she sleeps maybe 2 20 minute naps a day! Not only that but during the night she wakes at least 3 times where as before she woke only once and when she wakes for her 4am/5am feed she stays awake for the day! (This is that I put her down for the night at around 9) I'm literally going insane cuz I'm exhausted, in a sahm and my husband is out 12 hours of the day! Please help!!!