According to Wikipedia, there have been four declared wars between India and Pakistan. None of them were "won" or "lost" in that neither party in any of these wars was forced into unconditional surrender (as happened in, for instance, WWI and WWII).
That being said, it's fair to say that Pakistan did not fully achieve any of their strategic objectives. In summary:
1947: Pakistan was concerned that the Maharaja of the princely state of Kashmir and Jammu would accede to India, as such independent principalities had the option of joining either India or Pakistan. Pakistan intervened in Kashmir's internal strife to support a Muslim group trying to force Kashmir to join Pakistan. Instead, the Maharaja joined India in return for its military support. After the war, India controlled about 2/3 of the state, while Pakistan controlled the remainder.
Goal: Ensure that Kashmir and Jammu choose to join Pakistan.
Result: Most of the country became part of India, at least in part due to Pakistan's attack.
1965: Pakistan again launched an offensive against Indian-controlled Kashmir and Jammu. India responded by attacking West Pakistan. It is generally opined that India held the upper hand when the US and USSR brokered a peace treaty.
Goal: Take Kashmir and Jammu from India
Result: No change.
1971: India responded to political strife between East Pakistan and West Pakistan, prompting West Pakistan to retaliate directly against India. India's border held firm, and East Pakistani forces with their Indian allies created the independent nation of Bangladesh. In the skirmishes, where losses (especially East Pakistani) were tragically high, India gained control of about 15,000 sq. km of Pakistani territory, most of which was gifted back in 1972 as a goodwill gesture.
Goal: Maintain control of East Pakistan.
Result: East Pakistan becomes Bangladesh, out of Pakistani control.
1999: Pakistan attacked India and won some territory in the Kargil district. India retook most of it in the next two months, and Pakistan withdrew from the remainder under international pressure.
Goal: Take territory from India
Result: No change and heavy losses
So these conflicts could be considered "lost" by Pakistan in that they did not achieve their objectives, and in at least the 1999 war took significant losses; however, "lost" remains a difficult notion to quantify without an unconditional surrender. Pakistan could reasonably claim that it didn't lose even the 1999 war, but instead withdrew for diplomatic purposes.