I have a gap between my first two middle teeth in the front most doctors told me that theres a tissue that separates them, while the others are fine ?

The labial frenulum : The labial frenulum often attaches to the center of the upper lip and between the upper two front teeth. This can cause a large gap and gum recession by pulling the gums off the bone. A labial frenectomy removes the labial frenulum. Orthodontic patients often have this procedure done to assist with closing a front tooth gap.

Diastema: Diastema's (spaces between the teeth, can be corrected with orthodontics. Most diastemas self correct by the age of 18 (only about 7% remain). If you have spaces, and you don't like them, see an orthodontist. The tissue is sometimes fibrous and can contribute to the spacing.

Midline space: Could be due to tissue, thick maxillary labial frenulum. Best Rx ideally position teeth first, then reshape tissue. Can also be due to malocclusion (bad bite) or abnormally small upper incisors. Consult with Orthodontist.