I assume you are talking about chemotherapy. If so, it takes different forms, at different times, and people have different reactions.
Very generally, it does seem to be cumulative in effect, so what you say is not surprising. I doubt there is anything they can do about it much directly. It works because it presents a real challenge to your system. That challenge will be reflected in how you feel.
Best of luck. Be sure to stay in touch with your team, and contact them if you are at all concerned about any particular reaction.
For example the tiredness you refer to might have to be accepted, or might be dealt with by a less aggressive or even different chemo treatment. There needs to be a balance found, and they can only find it if you tell them how you feel.
Best of luck anyway. Remember that to a degree, this is your choice. It may be between two unfortunate outcomes, but it remains your choice.
