Is it common to try to find different words when blocking?

Yes, that's very common.... and the essence of what is for some "covert stuttering". My advice is not to give in to the temptation to find new words. It can become an agonizing mental gymnastics ... I would recommend to get specific guidance form a specialized SLP. One technique I find very helpful is voluntary stuttering. Allow yourself to stutter on those words by actually "imitating" the way you would normally stutter, only YOU are making it happen instead of letting it happen to you... It often turns into "effortless stutter" that allows for good communication.