Hi, I'm 23 year old male. I have been taking claritin D 24 hour for the past 3 days for my allergies. I have been feeling weird when I take it. I feel tired but anxious and a little tightness in my chest or a faster heart beat. I was with a girl last night and for some reason I couldn't maintain an erection. I've never had that problem since I'm healthy anf have been having sex for years. Is this due to the claritin or is it something else. Please reply with solutions or recommendations. Thanks