"I am definitely in the form of my life," Collins told the club website (www.whufc.com). "I do not know what it is, just getting better with age I guess."
Collins, who recently signed a two-year contract extension, has been a critical part of West Ham's defence this season averaging more than eight clearances a game, the highest within his team.
"It was huge to sign a new contract, the thought of leaving the club again was getting me down a bit," he said.
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"I was fourth choice centre-half at the start of the season, the gaffer (manager Slaven Bilic) told me that.
"I just thought the least I could do was get my head down and work hard in training and if the opportunity came along I would try and do well."
Collins was confident he could carry his form into the Euro 2016 finals in France.
"It (the Euro) is obviously something I am really looking forward to for the summer," Collins added.
"To be part of a team that has qualified for the Euros is massive and hopefully I will keep my form high and have a chance to start for Wales."
The Hammers take on Wolverhampton Wanderers in the third round of the FA Cup on Saturday, before travelling to AFC Bournemouth in the league three days later.
(Reporting by Nayan Das in Bengaluru; editing by Amlan Chakraborty)
