That really sucks! Without anything else to go by, something that strikes me is that you are sending out a huge number of resumes and your conversion from resume to interview is low.

As most resumes are screened initially by an HR person, your resume is probably being binned before anyone from engineering sees it because you don't have a degree. This completely sucks but is the reality.

Therefore, your best bet if you're looking to change strategy could be to narrow how wide you cast your net a bit and focus more attention on each individual application. Sounds like you've got passion by the bucketloads and engineers love people who love what they do. So try and find some engineers - are you going to meetups?

Meetups are a great way to get some informal time to meet people from the local community and learn what's in demand and what opportunities are going. More importantly, they're great places to learn a lot of information rapidly for free.