I am a gastric bypass patient. Drs have told me can't take aspirin to prevent a stroke?

Depend. Depending on which type gastric bypass (sleeve gastrectomy vs roux en y vs gastric banding) also may be you have bad stomach ulcer that prevent you from taking aspirin. Please call you surgeon/doctor and ask for the explaination on your case.
aspirin. A baby Aspirin a day is usually acceptable. Taking bigger doses for pain control, headache, etc. Can be too irritating to the gastric pouch and cause an ulcer to form. If there is a concern with the baby aspirin, just take a proton pump inhibitor daily to protect your stomach (ie prilosec, nexium, (esomeprazole) prevacid, protonix, dexilant).