How do you know if you're allergic to sterling silver?

My boyfriend got me a sterling silver promise ring (we don't have a lot of money) and I got it on Valentine's Day. About a month ago, so May I got these weird red itchy bumps on my finger right where the ring was and in the crease between my ring finger and middle finger. So I switched fingers and put it on the ring finger of my right hand and now after a month that finger started getting bumps and itching. Is it possible that I'm allergic to it? And if so why did it take 3 months to even develop anything? Also what can I do so that way I won't get those itchy bumps is there anything I can put on it or soak it in? I love this ring, a lot help!