As per U.S. DOT Regulation §399.87: Baggage allowances and fees:
For passengers whose ultimate ticketed origin or destination is a U.S. point, U.S. and foreign carriers must apply the baggage allowances and fees that apply at the beginning of a passenger's itinerary throughout his or her entire itinerary.
This means that the baggage allowance cannot change throughout the journey; there must be only one single baggage allowance that applies to the entire journey.
Also, as per IATA Resolution 302, the baggage policy of the marketing carrier of the most significant route (the first to cross continental "zones", in this case the BOS-DOH segment) applies to the entire journey.
In this case, the marketing carrier of that flight is Qatar Airways (since that flight is noted as a QR flight on your booking confirmation), and their policy for journeys to and from the U.S. is two free bags, weighing 23 kilograms.
Therefore, for your entire itinerary, you should be allowed to check two free bags, weighing a maximum of 23 kilograms each.