How do I go about getting into the engineering field with only a design degree from almost a decade ago? Due to health problems, I wasn't able to study well enough during my teenage years + 20s and I did not study or pursue something that truly interests me; instead I just graduated with a degree because it was easier for me at that time. My passion has always been in science - especially Robotics/Engineering or Physics. It has been bothering me for years and I know I can't get this thought out of my head unless I give it a try. I've been saving up money to study again and now I have the chance to do it, but I don't know how or where to start, not to mention I don't even know if it's "wise" to do it in my 30s. 

My thinking is to ultimately get into a graduate program at a decent school; but before I do that, I'll need to have a foundation in math and science, and possibly a second degree in engineering or some relevant field. I tried so hard to find a school in the US that offers second degree in engineering but still didn't have luck, except for the ones that are less reputable in this field, and I'm not sure if it's going to be a problem when I try to apply for a more reputable grad program. So I assume it would probably take me 5-6 years. And by the time I graduate, I will be in my late 30s. I'm not worried about how much time I'm going to spend but I need to know if it's a field that welcomes older people to seek entry level employment after they graduate. Is there anything wrong with my "plan"? If so, what would be a better approach for me to do this? Any recommendations on schools/programs and how to go about it is highly appreciated! Thanks a lot!
You have a Bachelor's already, which already makes you nominally qualified for graduate school! What comes next is figuring out how to make an entrance into the field when you don't have a background in it. The Bachelor's system currently in existence generally requires a basic education requirement, so I wouldn't suggest going for a B.S. in physics or engineering. I would instead suggest one of two things, combined with a healthy regime of self-teaching:


Simply take courses at a local institution
Get an associate's in physics or engineering


Would this make you a non-standard applicant, having your most recent degree be an associate's, or a bevy of post-bac coursework not for a degree? Well, yes, but you're still qualified. You're really quite young within the camp of non-traditional, older students. If you can back up a shorter (cheaper!), more focused set of courses with some experience doing applicable work (volunteer at a lab, try to land a position as a tech at a nearby school), that makes you just another applicant, albeit one with very different life experiences. 

There is a guy in my research group who has a wife and kids who transitioned into engineering when he was 30, and he swept right into an M.S. and then a Ph.D. program without getting a transitionary degree after eight years of no classes. It's definitely possible for top programs, as we're at a Top 15, but I would advise trying to get some experience and insight on the field at local institutions.