This is crazy! I'm having the exact same thing happening to me! The doctor subscribed me to a pill that was to clear my acne, and I did NOT even ask for it!!! (  Doxycycline) Ugh I regret this so much, I should of refused these pills. I took the pills at night, on an empty stomach , without water, (she never told me that I needed water) thinking it didn't matter, and also laid down for bed right there (she also didn't tell me to wait before going to bed)! I did everything I wasn't supposed to! I'm just so upset because I don't even care about my acne, and now I'm possibly at serious risk here. I'm honestly scared because I don't want an Ulcer and to get surgery for it. I'm awake right now, and the pressure/tightness in my lower chest hasn't gone. There's so many mixed answers here that idk what to do. I'll just go to bed first and see if it subsides with in two days, and if not I'll check back to my doctor. I'm and 18 yr old female btw.