Teething baby

How long does this last?! Months? I want my happy baby back. Today at work he wanted me to hold his " sing-a-ma-jig " over him and push the button over and over. if I stopped he would literally scream every time, Such an easy fix yet when trying to work, not so easy.
And he just wants to bite. We've bought him everything under the sun, mesh bags to put apple or ice in, Teething fridge rings, teething necklace, gel, sippy cup for a lil cold water, new bibs for all the drool, he just wants something in his mouth to bite. He fell asleep biting a toy and it kept falling out his mouth, so he'd wake up and shove it back in, clench down and fall asleep again. Becca snapped a picture. silly sad guy.