Answer above is correct, but as i am almost totally sure the spanish you are in contact is southamerican.......Gallego= immigrant/newcomer from Spain (especially in Argentina). This is because the big majority of immigrants from Spain in Southamerica were from the area of Galicia, people with cultural peculiarities - in fact, they share more with portuguese than with spanish, their own language and a strong accent when speaking spanish. So, "galleguito" is a diminutive and a pejorative at the same time. If you find comics of "Mafalda" by argentinian Quino, one of the main characters is a "gallego"....also, just for info,,,Fidel Castro is from galician origin. (Castro being a name totally galician...ex...Castro Street, Miami,,,center of cuban dissidency in USA)..etc...

Galleguito(a) is the diminutive form of Gallego, which is a person from the region of Galicia in Spain

to your last comment: it is quite possible...it is common that sometimes couples in love tell each other a bit despective adjectives in a very tender way to show that their affection is bigger than - lets say - some external "realities".