Should I pursue chemical or biomedical engineering at this point?

Hi, Katarina, I can think of a couple of different ways to move forward in this situation.  I hear what you are saying about not wanting to lose momentum in academics - you're using a specialized skill set right now. Once folks start working full-time or part-time, they can be too tired/drained to put enough energy into the additional work of studying and learning.  You might consider looking into obtaining a Master's degree in a field that is closer to the interests you have discovered as you've grown.  Depending on your chemistry/biochemistry background, you may need to take some extra courses to prepare you for graduate work in your new field (your graduate advisor would work with you on this), but your modeling skills might be very much appreciated by folks who are interested in molecular modeling.  A Master's degree typically takes two years, possibly three depending on whether you do a thesis or not, and how your research and thesis-writing goes.  And, you get to focus much of your time on an area that excites you intellectually, which helps keep you motivated.  There's generally less emphasis on ticking off boxes for credit policies, and more emphasis on helping you learn what you need to learn in order to pursue the research and learning that you want to do.  I would encourage you to look into this option.

With your current degree, you might also be competitive for a job doing modeling or mechanical analyses for a company that makes medical products or devices.  Over time, you could focus some of your professional development efforts on learning more about the chemistry involved in your company's devices/products.  You could discuss this as a potential area of growth with your supervisor.  You might be able to bend your career arc to include responsibilities beyond just mechanics.  This is dependent on a lot of external factors (what products the company makes, the degree of flexibility in their system, the types of chemistry involved in their products, etc.), so while I can imagine this could be possible, it's not as much under your control as pursuing a Master's degree is.

And once you start an MS program, you can think about carrying on toward a PhD.  That's a different discussion!!  ;)  But in general, I think advanced higher education is a great way to adjust your qualifications and credentials to better align with interests that you develop as you mature.