- So this is the root verb to like (7abba): حبّ
- Then this is a derived verb of it (which really has the same meaning in English) (A7abba): أَحبَ
- Now present first: I like (A7ibbu) أَحِبّ
- And the derived I like (U7ebbu) أُحِبّ
Your confusion is in the fact that the present, looks like the past derived, but notice that 1, and 3 are rarely used. The derived verb is more known in this case, so A7abba: he liked, U7ebbu: I like.
https://qutrub.arabeyes.org/ (type a verb and see all of its shapes)