If i use a plastic bottle(aquafina) to carry around water and refill it throughout the week should i buy a new one after a certain period of time? should i use a tumbler, are there any health concerns i should be aware about?

Health concerns!: There are health concerns you should be aware of if you reuse water bottles. Bacteria can grow in the water bottles & so if you plan to reuse them after each use they should be cleaned with with soap & hot water, the same as when you clean cups after a meal. Otherwise use a new bottle each time. If you instead use a tumbler than clean that often! I wish you well with your health!