Tampons and Vaseline

So, I am 19. I started my period at around 12 or 13, and ever since then I have always worn pads. I have tried tampons maybe once or twice before, but each time I just gave up because I could not figure out how to put it in and/or it hurt. I have a hard time relaxing as well while in the process which makes it even harder to insert the tampon inside of me. I have always been really cautious when it comes to sticking things into my vagina. I have never even masterbated before because I have always had this fear of possibly cutting the inside of my vagina by accident (especially since I like to keep my real nails long). My current boyfriend of 2 1/2 years has fingered me a few times since we've been together (we are both still virgins) and each time it felt great. However, I just can't bring myself to do it alone. I don't know what is wrong with me. I am very educated on my reproductive parts, but I want to grow more accustomed to my own body and what works best for it. So, I want to start by learning how to use a tampon because sometimes pads are just so uncomfortable. Especially when I am out and about. My mom bought me the small tampons (for beginners I assume). She suggested that I add a tiny bit of vaseline at the top of the applicator for a better ease into my vagina, but I am afraid. I don't want to get some sort of infection or anything. Has anyone ever tried vaseline when inserting a tampon for the first time (or at any time)? Did it make it easier to slide the tampon in? Did it give you any sort of infection or irritation? I have very sensitive skin already. I have also read and researched how to use tampons, but I still just can't get the hang of it. Any advice, tips or tricks would be greatly appreciated. Thank you in advance. :)