super fussy 5.5 month old. help!

My 5 1/2 month old has been extremely irritable & difficult to soothe. He was sleeping from 8-2am waking to feed then typically back down until 6/7am. This week he has been waking almost every 1 1/2 to 2 hours & I'm one tired mama. Luckily my husband is a HUGE help to me & has taken shifts to allow me to rest but we ALL need our sleep. Any suggestions or advice to what could possibly be going on?!