Unfortunately for you, I'm about to do some ranting and scolding. But first, a story.
When I was in my mid-twenties, I decided that I needed to go to the dermatologist purely for reasons of vanity. I wanted a professional to look at my face and let me know how I was doing, and possibly get a prescription for Latisse. I figured: I'm young, I have no moles on my body, (just a few freckles) and I have worn sunscreen every day since I was 14. There's no way they will have anything to say to me except maybe that I should start using eye cream more often.
As I'm sure you can imagine, I was dead wrong. I had not one, not two, but THREE suspicious looking freckles that needed to be biopsied to see if they contained pre-cancerous cells. I was shocked. Looking back on it, I don't know why I was so confused. My dad and grandpa have both had several basal cell carcinoma removals in the past twenty years, but I chalked that up to my dad roasting himself in baby oil in the seventies. I had been sitting exclusively in the shade since I was a child and figured I was safe.
Luckily, my biopsies all came back negative for pre-cancerous cells and other than a bit of discomfort and some small scars, nothing ever came of it. Around that same time, my sister who was in her early twenties figured she'd get herself checked out as well, and her biopsies did show that she had pre-cancerous cells in a mole on her shoulder. She had to have a pretty invasive procedure to remove all the surrounding cells, and it left her with a pretty badass scar.
What I'm trying to say here, is that no amount of prevention can truly keep you safe from skin cancer; sometimes it's just gonna come up. What you can do, however, is stay on top of regular appointments to get your moles checked out by a professional, so that you can catch any problems that may arise as early as possible. You'd be surprised how common it is to find a suspicious mole. I made Theo go a few years back and he had to have a couple biopsies as well.
I know it's a huge pain in the ass - going to the dermatologist is not cheap, even if you do have health care. I urge you to make it a priority and save up for it if you can. If you can't go to a dermatologist specifically at this time, see if your GP will give you a quick once over when you visit. I've even asked my gynecologist if she would mind taking a look at my freckles, and she's always been happy to do so.
In the meantime, you can keep an eye on your moles by following the ABCDE's.
Asymmetry: You want your moles to look the same if you were to fold them in half.
Border: Look for any uneven edges that may be a sign of a malignant mole.
Color: Most benign moles have only one color, having a variety of colors in a single mole may be a warning sing.
Diameter: Melanomas are usually larger in diameter, bigger than an eraser on a pencil.
Evolving: Most moles stay the same, but if they are changing in size, shape or color over time, you will want to get it checked out ASAP.
Do yourself a favor, and get yourself over there as soon as you can and make it a priority to go regularly. Learn how to distinguish good moles from bad ones, and remember that you are your strongest advocate when it comes to health care. I want you to live forever, like the kids in Fame.