Lindsay Lohan claims she isn't a big drinker and has only done cocaine "maybe four or five" times ... but boy does she love herself some ecstasy.

Lohan sat down with Piers Morgan late last month for an interview that just appeared in the Daily Mail and if you believe her ... we're all crazy, because she doesn't really have a drug or alcohol problem.

Here are the highlights:

-- She got advice about controlling her drinking from Heath Ledger. He told her he had given up drinking for a full year so she took his advice. She says she has no prob giving up alcohol.

-- She hasn't taken a drug (other than her prescriptions) in a year.

-- She's not an alcoholic and can give up drinking.

-- She's taken cocaine "maybe 4 or 5 times in my life."

-- She likes ecstasy better than other drugs.

-- She does not think she needs to be in lockdown rehab for three months.

-- She thinks rehab will be good for her because it gives people time to just be by themselves.

-- She's straight.

-- She calls Dina "mum."

So we gotta ask ...