A hickey is a mark of having been intimate with someone. Only the wearer knows what has really happened but everyone who sees the hickey can jump to her own conclusions.

To you at first glance, it might seem like your mom is really over-reacting to the situation. Leaping from a hickey to the conclusion that you're having sex could be a bit overboard. But all she has seen is the hickey and being confronted with such visible evidence of your sexuality could be a bit shocking and anxiety-producing.

So, I think you should try to be understanding of your mom's reaction, anxiety, and concerns at this point. Your goal now is really to assure her that you are thinking carefully about your actions and decisions at this point in your life.

Talking to your mom about something she is already so sensitive about might be difficult, so it's also a good idea to remind your parents that you are trustworthy in many ways and maybe things will translate into the boyfriend area as well. You could try things, like calling to let them know where you are or telling them what is going on in your life, to let them know that you aren't trying to deceive them. If you are patient with your mom and prove to her that you are trustworthy, hopefully she won't leap to so many drastic conclusions about what you are doing or what you may do in the future.

Since the subject has already been broached, you might want to use this opportunity to speak with your mother about sex, explaining very carefully what point you are at or what you are comfortable talking about.

Overall I think you just need to be patient and, if you are open and up front, maybe when your mom calms down and the hickey disappears, seeing your boyfriend won't be such a big issue.

Finally, since it seems that visible hickeys aren't such a good idea in your family, you might want to think about ways of avoiding them in the future.