Without being familiar with your particulars I couldn't say, but depending on what your design experience was I wouldn't have a problem if you self-identified as an engineer. Here's what NJ says:
The terms "practice of engineering" or "professional engineering" within the meaning and
intent of this chapter shall mean any service or creative work the adequate performance of which
requires engineering education, training, and experience and the application of special knowledge of
the mathematical, physical and engineering sciences to such services or creative work as
consultation, investigation, evaluation, planning and design of engineering works and systems,
planning the use of land and water, engineering studies, and the administration of construction for
the purpose of determining compliance with drawings and specifications; any of which embraces
such services or work, either public or private, in connection with any engineering project including:
utilities, structures, buildings, machines, equipment, processes, work systems, projects,
telecommunications, or equipment of a mechanical, electrical, hydraulic, pneumatic or thermal
nature, insofar as they involve safeguarding life, health or property, and including such other
professional services as may be necessary to the planning, progress and completion of any
engineering services. The design of buildings by professional engineers shall be consistent with
section 7 of the "Building Design Services Act," P.L.1989, c.277 (C.45:4B-7).
If you've done the above, I'd say you're an engineer.
Actually, in NJ depending on the level of design work you've done, you could have gotten your PE license without taking a single engineering course. It just required 20 years (IIRC), a ton of documentation and passing the test. Now you have to have a 4-year degree in engineering or engineering technology plus 15 years. But that's all about being a PE; "mustang" engineers are engineers all the same.