Mahatma Gandhi might have fasted but not for country and for issues of national Importance. As his fast and Nehru's fight (Independence) were baseless so method of propganda was used. That is the reason you will not get any consolidated information. Here I have compiled the detail of Gandhi Fast mentioning why, when and where to let you know the truth.

Years of Fasts of Mahatma Gandhi
1913 (Phoenix)	Penitential fast for a week for moral lapses of two immediate at the settlement
1914 (Phoenix)	Fourteen days fast for similar reason
01 June, 1915	Fasted for a day on detecting untruth among Ashram boys
11 September, 1915	Gave up evening meal due to some Ashramaties objection to the admission of a Harijan in the Ashram
15 March, 1918	For a rise in the wages of mill workers of Ahmedabad
06 April, 1919	First day of Satyagraha fight
13 April, 1919	Began fast for 72 hours for Jallianwala Bagh massacre at Amritsar and disturbances at Bombay and Ahmedabad.
19-21 Nov., 1921	Fasted owing to disturbances at Bombay
28 November, 1921	Took vow to fast for 24 hours every Monday till Swaraj was won and started it from that day.
12-16 Feb., 1922	Owing to the massacre at Chauri Chaura
17 Sep. to 7 Oct., 1924	For communal unity
24-30 Nov., 1925	For having detected sexual aberrations in some boys and girls of the Ashram.
22-24 June, 1928	Owing to moral lapse of an Ashram inmate
20-25 Sept., 1932	In protest against the decision to setup separate electorate for the Harijans.
03 December, 1932	In protest against Government not allowing a fellow prisoner to do scavenging work
08-29 May, 1932	For self purification and of his colleagues.
16-22 August, 1933	In protest against Government’s decision not to grant all the facilities for Harijan work which he was having previously in Jail.
07-13 August, 1934	An irrate reformer attacked an opponent of the Harijan upliftment movement with a lathi. Started fast to atone.
03-06 March, 1939	For the breach of promise by the Rajkot ruler.
12-13 Nov., 1940	Fasted for two days for minor thefts in the Ashram
05-07 May, 1941	Because of communal riots in Bombay and Ahmedabad
29 June, 1941	For communal unity
10-03 March, 1943	In protest against Government’s propaganda that the responsibility of disturbances after Quit India resolution was that of Congress.
30 November, 1944	Fasted or thought of fasting for one or more days. Details and reason could not be traced.
20 October, 1946	Probably on account of an error by the person who prepared the fair copy of a letter written during negotiations with the Muslim League.
15 August, 1947	Against partition of the country
01 to 03 Sept., 1947	For communal harmony
11 October, 1947	Birth date according to Vikram calendar. Fasted instead of celebrating it.