What Causes Brown Colored Vomit After Taking 'excedrin'?

so heres the deal: for the past 4 days or so, i've been drinking. the first 2 days i was heavily drinking, the last 2 days it was light drinking. on top of this, days 2 and 3, i took morphine, which has made me completed constipated(1 movement a day, and not much fecal matter when the movement happend). so, today(day 5) is my problem: i got up, ate 3 slices of wheat bread, slept for 2 more hours, woke up agian, took 2 excedrin, mowed the lawn(45 min) and then immidately went to work out(roughly took 1 hour). it was a fairly intense workout- was covered in sweat, breathing heavy for 5-10 min. and feeling like i was going to throw up: i went to throw up, and threw up a brownish bile, which i believe had tiny chunks inside. i imagine i was most likely bleeding from my stomach, but wanted to know if that was due to excedrin + heavy workout, or if it might be something much more serious. sorry for the wall of typing, but i like to give every detail possible haha. thank you for your time