The 33-year-old requires surgery to tackle a hernia problem after already undergoing a hip operation, which caused him to miss the recent tour of India and leave the pre-Christmas trip to Pakistan early.
He will now miss the Test and One-day series against Sri Lanka but is hopeful of returning to action by mid-July to face Pakistan.
"I'm a lot more confident and happy now that we seem to have put our finger on the reason I've not been able to rehab properly," the Warwickshire player told BBC Five Live.
"We were looking at another hip operation, which is a lot more major surgery and a longer process to get back - probably three months.
"This, I'm told, should be six weeks and I'm back playing.
"The Ashes will be coming up so it's important I get back playing as quickly as I can, for my own good so I'm bowling for the good of Warwickshire and England.
"Of course there's competition there now so I have to get back playing early to get my place back."
Giles said he was glad to have gotten to the bottom of the injury problems which have been plaguing him over the last year.
"I got some strange looks in the waiting room, there were other people waiting to see the specialist and I sort of cheered and said 'I've got a hernia, great news' and I think they thought I was a complete nutcase to be honest.
"I'm not sure of dates exactly but by mid-June I could be back playing properly. Saying that, I'm going to miss Test matches, I'm going to miss some cricket, but again going back to what my season looked like, it is a lot better news and I'm just dying to get back now.
"The sun will be out then and the pitches will be dryer, so it would probably be the best time to wheel me out."
In the meantime, his established role in the squad is likely to be filled by the promising Monty Panesar - who did enough in three Tests against India to suggest he can become a long-term replacement for Giles.