Look into backpackers tents as they are designed specifically to pack down as small and be as light as possible.
I purchased the REI Passage 2 tent for my upcoming cross country trip. I've tested it indoors but haven't had a chance to do a pre trip real test like I wanted but from what I can tell I made a good choice. On a budget I think its one of the better tents out there if not the best and I did a fair amount of research and reading reviews before deciding. Either way check out REI.com and if you have one near you absolutely go in person so you can see how small and light the tent packs down for yourself. If you can't REI puts all that information in the specs so you can still get an idea.
As for carrying it along I have a Givi 45 litter top case and soft saddle bags (kind of wish I had saved up for the Givi side cases instead) but still plan on tying it down to my pass seat so as to not take up too much space elsewhere (I'm going to be away from home for a few months and can use all the space I can get).
William mentioned that he got an air pad and I did too, the “ Exped SynMat UL 7Air Pad" also bought on REI. In my opinion its way more comfortable and packs down a lot smaller (somewhere around the size of one of those reusable water bottles you might bring with you) than the traditional pads I remember using a bunch of years ago hiking with an avid backpacker friend I had at the time.
William: Just curious, where are you headed for 6 weeks? That's a long road trip lol. I'm going to be gone for awhile cause I'm actually going to stay in LA area for 2 months plus about 1 month on the road round-trip.
