CHICAGO – Derrek Lee knows the reason why the Cubs are winning now.

Lee broke a streak of 126 at-bats without a home run with a three-run shot in the second inning to help the Chicago Cubs complete a three-game sweep of the Houston Astros with a 7-6 victory on Sunday.

The Cubs have won 15 of their past 19 games and swept the Astros in a three-game series at Wrigley Field for the first time since May 1984.

The Cubs fought back from a five-run deficit in the second inning.

“We’re playing with confidence, regardless. We never felt we were out of the game,” Lee said. “We knew we had a good team, but now we have that confidence to go along with it. There was a time where we got down like that we might not of been sure that we could come back.”

Ryan Theriot and Angel Pagan also homered for the Cubs, who remain 3 1/2 games behind the Milwaukee Brewers in the NL Central.

“The club is gaining confidence and that’s the important thing,” Cubs manager Lou Piniella said. “They’re playing with confidence and confidence is a good thing.”

The Cubs used five relievers to preserve the victory, who combined for five scoreless innings.

Reliever Michael Wuertz (2-2) earned the victory. He got one out in the seventh with the bases loaded and pitched a perfect eighth inning. Bob Howry earned his fifth save.

Mike Lamb homered for the Astros, who have lost six straight on the road.

Astros starter Wandy Rodriguez (6-8) couldn’t hold an early 5-0 lead. He allowed six runs on seven hits in the second inning. With one out, Mark DeRosa doubled and scored on Geovany Soto’s single. On the next pitch, Pagan hit a two-run homer. It was his fourth of the season. Jason Marquis and Theriot followed with back-to-back singles. Then with two outs, Lee hit a three-run home run into the left-field bleachers, giving the Cubs a 6-5 lead. It was his seventh of the season, his first since June 3 against the Braves.

“It’s been a long time,” Lee said. “It felt good, plus it gave us the lead and put us back in the game, so it felt very good.”

Rodriguez was coming off an impressive four-hit shutout of the New York Mets on July 6, but left after 3 1-3 innings. The lefty gave up seven runs and nine hits in his shortest outing of the season.

“He got in situations where he didn’t use his breaking ball or couldn’t use his breaking ball, and they hit his fastball,” Astros manager Phil Garner said.

Marquis, who started for the Cubs, didn’t last long. Lamb tied the game with a solo shot in the third inning off Marquis. It was Lamb’s eighth of the season.

Theriot’s leadoff homer in the fourth inning broke a 6-6 tie.

Marquis went four innings and gave up six runs on six hits. Marquis’ ERA in his past seven starts is 6.75.