if u ask me, i dont think u should change your meds, 100mg doxy twice daily is more than fine, at this stage it matters to take it longer than in hi dose. u dont have disseminated lyme, so your bacteria is in blood or very close to blood tissues and easily killed by doxy. and no biofilms.
if u take 400 u may end up with gut issues , have to stop meds then u can be in trouble for a long time.... if u want to go that way, 300 is really more than enough this early and again, risks have to be taken into account.
u can be cured from it at this stage... while u take the pills i would go find an LLMD, u have time to win the battle early.
fyi vancomycin is way better than doxy at killing lyme and gives u almost zero chance of relapse this early. but good luck convincing your doc u need it, it is considered a reserve abx for serious infections that can kill u.
/youtu.be/KCxA0Vmqb2oour lyme disease is not serious enough, patients when it comes to lyme and medical community, are of two types: whiners....or dead... there is nothing in between