The 27-year-old scored his third goal in three games on Thursday evening to help the Cobblers beat Cheltenham Town in the first leg of their League Two playoff semi-final.
The Irishman has scored six goals in 17 appearances for Town since joining from Coventry City in January.
O'Donovan told BBC Radio Northampton: "I said after Rotherham in February that it was going to take a bit of getting match fitness.
"I just want to play more games. I want the season to go on and on.
"I'm on a good spell of form now. I'm starting to feel good now, feeling fit and sharp, and getting the odd chance."
Northampton travel to Cheltenham for the second leg of the playoff semi-final on Sunday.