Can I stop Minoxidil and continue with Finasteride ?

You are right to be concerned.While minoxidil works for some, the problem with the medicine is that
it does not stop hair loss, and the DHT will continue is binding to the
hair shaft which will eventually overtake any additional growth caused
by the Minoxidil and die, perhaps just slightly later than it would have
without the medicine.
Also, the alcohol base required to support the active ingredients
also cause irritation of the scalp and severe reactions for many people,
such as the increased shedding you are describing. The fact is that it
does not work for everyone.
In addition, side effects reported for
brands like Propecia/Finasteride are the result of hormone imbalances
caused by standardized dosing of those medicines in oral form.
The
number one first step I recommend is a comprehensive consultation with a
hair regrowth specialist who will perform lab tests to determine the
underlying cause of your thinning. Without labs, no-one can really know
what your true cause is and any treatment will be temporary at best. From here, you can receive the best treatment for your case. It is also worth noting that any medicine that actually can make changes inside your body, are
required under the FDA to be available by prescription only. This
therefore means that it is not possible for anything that does not
require a prescription to cure or prevent hair loss or regrow thinning
hair. Thus, a personalized medicine will be the best choice because
instead of a "one size fits all" approach, you will be taking something
which is truly catered to your body's needs.
The treatment is out there. Good luck on your search.

The safe answer would be to continue using both as if you stop the Minoxidil then you are likely to lose the benefit gained from it. With combination therapy the science would support that Finasteride is doing most of the heavy lifting. In practice I have found some men able to discontinue Minoxidil after a time, while staying on Finasteride, and still having a good result. I would recommend you discuss this plan with a qualified hair restoration physician.