Took (zantac)ranitidine last night and today feel tired/groggy and short of breath?

I didnt even realise these were side effects until I just looked them up now so dont think it could be in my head. I actually noticed earlier today that I keep feeling the need to take deep breaths like Im not getting enough oxygen, and I also feel REALLY quite groggy and tired. Thought it may be dehydration but perhaps its the ranitidine I took last night?