The midfielder returned from a month-long ankle injury lay-off in Saturday's 3-1 home FA Cup defeat to Bournemouth, who got the all-important first goal at Brunton Park as the Cumbrians slipped to a fourth defeat in their last five games in all competitions.
Thirlwell told the club's official website: "When we concede at home at the moment we do lose a bit of confidence.
"We're struggling to get wins here and we talked about the next goal being massive when we went in for half-time. We got that, but they killed it off with their late sucker punch.
"I don't know if the home form is preying on people's minds, but what is certain is that something isn't happening here.
"We have to find the answers for that as a group of players because the preparation for the games has been right.
"We knew all week what we were going to have to do to stop them from playing, but we didn't take that on to the pitch. We have to accept that criticism."