The London club have had a mixed start to the new Premier League season, with a 3-1 loss at home to Manchester City last weekend leaving them in 15th place in the table.
And with that defeat signalling the third in their last four league games - with a shock 3-0 victory over Tottenham sandwiched in between - Tomkins is keen for a return to winning ways.
"It's not a case of doom and gloom (after the City match) and we're looking forward to trying to get back on track at Swansea," he told the club's official website.
"The Premier League is a funny league this season. There have been a lot of unexpected scores and on our day we can beat anybody.
"Swansea are good technically, but if we can play how we can, then we can get a result."
The 24-year-old, who struggled for opportunities at the beginning of the season, is also delighted to be back in the starting XI.
"It can be frustrating at times when you're sitting on the bench, but I'm growing in confidence with this run of games that I'm getting," he added.
"I love playing for West Ham and hopefully I can help us bounce back at Swansea."
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