Both sentences are incorrect. You can write it two ways: "I think I have to go to the hospital", or "I think I have got to go to the hospital" Both 'have to go' and 'have got to go' are interchangeable in this positive form when you are talking about something that is necessary. The first is probably slightly more common.

[1]I think I have go to the hospital If you're trying to say you may need to physically be at the hospital. You would say "I think I have to go to the hospital." To go is the action. [2]I think I have got to the hospital This sounds like you're saying you think you have arrived at the hospital. In any case, the correct way to say that would be "I think I have gotten to the hospital." However, "gotten" is an American word.

The correct sentence is: I think I have to go to the hospital.

If [2] use persent perfet ? has different meaning with simple present?