More and more freckles everywhere, and only 19 years old. Anything to worry about?

Watch sun exposure. Very fair skinned and red hair make people more prone to having skin problems if over exposed to the sun. The more sunlight in the summer, the more freckles. Do not by any means become a "sun recluse", you need vitamin d after all! See a dermatologist to have a baseline evaluation on your skin and embrace your feckles!
Freckles. I assume you are fair skinned and should be using sunblock every day and wearing a hat when outside, if not fair skinned, freckles are less of a worry.