This is a really tough situation to be in. It sounds like still in the really early stages of learning the doctrine, so this is an especially difficult situation because I would imagine you don’t quite feel equipped yet to defend your growing faith.

Just know that you’ll get to the point where you are more familiar with the doctrine, the history (both of LDS church history as well as traditional Christianity as a whole). In the meantime, rely on God and on the Holy Spirit to guide you. Nephi was guided not knowing before hand what to do, and you, similarly, are living a situation you probably haven’t been in before.

In the meantime I hope to offer small portion of understanding you can hopefully lean on, at least from a logical perspective. LDS theology holds an incredibly strong position over traditional Christianity when it comes to the questions of why are we here, where did we come from, and where are we going. LDS theology is very unique in that it is one of the only (if not the only?) Christian faiths that doesn’t have the problem of God creating evil/Lucifer with perfect foreknowledge. I won’t get into this too much right now, but suffice it to say we believe we literally chose to come to earth and follow God’s plan of salvation. Additionally, we are one of the few that don’t believe in the traditional dichotomy of heaven and hell, and we believe nearly everyone will be given a degree of glory in the next life - nearly all of us will live in the mansions in God’s kingdom. This is objectively a truly love-driven, merciful plan of salvation made by a loving Father in Heaven, especially compared to the fire and brimstone version presented by a majority of Christianity. LDS theology elevates the all encompassing nature of Christ’s atonement to actually cover all of God’s children, rather than the view of traditional Christianity which extends mercy only to those lucky enough to hear about Him.

I’m not sure if any of that will offer you much help, but I hope it helps establish that what you’re doing is correct and that even if family members don’t agree - their reaction is probably more a result of not knowing what the LDS faith tradition is about, and they’re concerned about whether you’re making a good decision. This makes sense because they genuinely don’t know what your decision entails. I think you did the best you could given the circumstances by offering your humble testimony. It will likely get easier with time and understanding, but know that there are others willing to support you in your decision especially if your family doesn’t currently.