Even after about 150 hrs, I do not have the nerve to do spins on my
own because I do not understand them well enough. I am comfortable
with stalls and unusual attitude recoveries of the kind that are
tested on the PPL test but have never done spins with an instructor.

If you are "comfortable" with stalls and unusual attitudes and don't
understand spins, I would suggest that you get some spin training or at

I am comfortable with stalls and slow flight in any configuration for
the cessna 150 and comfortable with the unusual attitudes my
instructor taught me for the check-ride. Basically they were just two
kinds taught - one where we end up in a steep dive and another one
where we end up "on top" close to a stall. I was tested on both on the
checkride. Besides these I am sure there is a lot of other stuff I
have no idea about which is why I mentioned that I am "comfortable
with unusual attitude recoveries tested on the PPL test". Maybe these
aren't even considered unusual attitudes, I don't know. It wasn't
meant to mean that I feel comfortable if the airplane suddenly flipped
over for e.g. What kind of unusual attitude recoveries are usually
taught beyond the PPL?

least a better understanding of spins immediately.
Feeling "comfortable" with unusual attitudes without a corresponding
knowledge of spins can be an extremely dangerous combination.
I would suggest strongly that you immediately begin feeling less
"comfortable" with unusual attitudes, or get some basic spin recovery
training as soon as possible. These two items are inseparable.

I do understand what causes a spin and how we enter one but not the
general aerodynamics behind it and I have not done one with an
instructor yet, I plan to some time. With the general level of comfort
I have with stalls and slow flight, I don't have that much fear of
stalling inadvertently and spinning. Of course I could be naive in
thinking that but that's what I feel.