Odd Teething Symtoms?

My 6 month old has been teething for quite awhile now. He is still sleeping relatively well except sometimes his naps are only 30 mins. The last few days he has been really fussy when he is usually a pretty happy baby. What is odd is he has been grunting and yelling a lot since Saturday and when he does this he stiffens his legs and puts his little hands in a fist like he is frustrated. Is this a symptom of teething or could it be something more? He doesn't seem to be having gas pains. Thanks!