It all depends on what you enjoy doing the most. If it's the structures, think about structural engineering. Just keep in mind that it will be mostly math and designing things on a computer, not building things with your hands. If you like contraptions that move, try mechanical engineering. But again, most engineering jobs are math and computer based (design jobs, anyway) and less on the actual building.
But it's a good living, and speaking as someone who got interested in engineering for the same reasons, you can find the same / similar satisfaction building computer models, spreadsheets, CAD drawing, etc. as part of design work. And there are actual engineering jobs that do get to build stuff, mainly in industry and maybe even in academics (professors / researchers). Most of us engineers have to watch other people build what we designed (or what other engineers designed), and those people often curse us for designing things they can't build. Or we curse them for not being able to build what we designed.