The Scotland U21 international notched his 12th goal of the season as he helped the Saints to a 2-0 Scottish Cup fourth-round win over Livingston on Saturday.
Peterborough failed with a bid for May in August and last week it was reported that Rotherham offered £300,000 for the player which was rejected by the Scottish Premiership side.
However, May continues to ignore all transfer speculation.
"I have started well and I have to try to continue that form," said the 21-year-old.
"I have more goals than I would have thought at this stage of the season which is good. But I am not looking too far ahead.
"The gaffer keeps me informed but I didn't think too much about that (Rotherham), I had no decision to make.
"I am happy playing for St Johnstone and learning my trade, I am playing every week, doing well so there is no reason to look elsewhere."