Why don't you be upfront with her! There are ways other than visiting a MP to contract the skin infection.
Have you read the info on www.Molluscum.com ?
"Molluscum Contagiosum can only infect a person with a compromised immune system. Even though Molluscum is very contagious, many couples do not transfer the Molluscum infection from one to the other. If you have any irritated skin that comes into contact with contaminated water from a swimming pool or spa, a contaminated shared towel, hotel bedspread, exercise equipment, toilet seat, or sleeping mat in day care, you can contract Molluscum if you concurrently have a mildly compromised immune system. If a person who comes into contact with Molluscum has a strong immune system, the Molluscum dies off before it can develop into any lesion."
So, tell her you had a cold, your dick was raw and chafed from wanking after dreaming about her for hours on end or some shit like that. Then you must have contracted it after going to the gym/pool/hot tub or somewhere like that. Be honest with her, well, almost.
She'll either understand and be completely sympathetic or she'll run screaming! Either way, she must be wondering why you won't let her suck your cock! She's bound to think something's wrong. Tell her!