Your body is not likely to react differently if you take the same medication, dose, and route you did the first time. Whatever made you susceptible to getting side effects from oral Finasteride has not changed.
You do have the option of trying topical Finasteride. There is less systemic absorption with the topical, which will likely result in less side effects. Start out applying a few times a week and SLOWLY work your way up. The goal is to have a regimen that you can tolerate long term, so don't rush it. Even if you end up with a 3x a week or EOD regimen, it's better than nothing.
Also, if you are not taking the full dose of a DHT inhibitor, make sure the rest of your regimen is spot on. Minoxidil, Ketoconazole shampoo, dermaroller, laser helmet, ect -- anything that has a realistic chance of helping you.
From JAAD (Journal from the American Academy of Dermatology" published in 2013:
"The PK (pharmacokinetic) profiles of finasteride after single and multiple doses of the oral formulation were consistent with literature data. As expected, systemic absorption and extent of exposure were much lower with P-3074 (topical finasteride) than with the oral formulation."
