There's a number of possibilities with these symptoms , most but not all of them related to diabetes, so best to ask to have them checked out.
Postural hypotension (auto nerve damage) can cause dizziness due to blood pressure not responding quickly enough when you first stand up from sitting etc. Trick is to take your time when first standing.
Peripheral neuropathy can cause difficulty in knowing where to place your feet and also cause leg weakness. Whether it could cause symptoms as severe as you describe not sure.
Spinal stenosis from any back or disc injury can cause leg weakenss when walking short distances.
Electroylyte/salt imbalance from persistent high blood sugars, poor blood sugar control. can cause severe muscle weakness and dizziness. As can anemia which can develop over time in diabetics as anemia of chronic disease. And of course having severe blood sugar swings can do much the same.
And of course intermittent claudication as previously mentioned.
If you're not eating properly and not controlling your diabetes the consequences will be very severe at a young age. Hopefully at your age it will be something they can fix.