Should I switch from Finasteride to Dutasteride or to increase the dosage to prevent my hairline?

Hello, good question.Dutasteride theoretically has more potency for hair preservation than Finasteride but a higher side effect profile as well.  The use of dutasteride for hair loss is an off-label use according to the FDA.  Typically regrowth of both agents occurs in areas where the hair is miniaturized and not where slick baldness occurs.  Consider the use of regenerative techniques such as PRP and others and the use of nutraceuticals such as Nutrafol which have a much better side effect profile.Best, Dr. Anil Shah

This needs an in-person evaluation. I suggest seeing a hair loss expert now to evaluate and go over your condition and provide you information about your best treatment options. There are great non-invasive options like prp/progesterone and/or hair transplantation. See an expert. Best, Dr. Emer

I would recommend looking into alternative options.
There are several known problems that exist when using Finasteride as a hair loss medication, lets take a look at each one:
    Finasteride only works for a short period of time.  It works for just a few hours a day (its half-life is 6 hours).    Finasteride does a poor job of actually blocking DHT production. In fact, it only blocks 1 out of 3 types of DHT receptors. That means hair loss is STILL taking place while you are using the medication. This combined with the short half life means that Propecia is about 60% effective at stopping DHT from thinning your hair.     Finasteride is not customized to the individual. Like millions of Big Pharma medications out there, the exact same dose of Finasteride is given to people who have different heights, weights and biochemistry. This means that men who want to stop hair loss for good can take the recommended dose of Finasteride every day, and experience nasty side effects for no good reason! While for other's their dose may be insufficient to even reduce DHT by the 60% it is rated at.Similarly Dutasteride is not FDA approved and is reported to have high side effect profile while not being completely effective at all for users.
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 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.
The treatment is out there. Good luck on your search.