Hi Heather, I've definitely been there, too. I know the fear, as I believe in a literal hell, as well, like kicker.
The one thing to keep in mind during all of this is that Jesus knows our hearts. While our emotions and thoughts may be fleeting, and feel like the exact opposite of what we truly desire, He knows our heart's desire and listens to its cries. When my obsessions were really bad, I couldn't pray at all, because I was just filled with horrible thoughts and feelings. So all I would do is pray the simple prayer that God would cling to me, and not let me go, because that was the true desire of my heart... not all this stuff that OCD was throwing at me. When you are in the midst of fear and obsessing, pray a simple prayer of peace. I know when my OCD becomes overwhelming, it's the only tool I have that brings relief from it all.
Know that nothing can tear us from the grip of God's love and his wonderful free gift of abounding grace. Like a never-ending stream of ocean waves crashing on the shore, God's grace is available for us without measure or merit. Y
our feelings of fear and doubt, however horrible and awful they are, will not determine what will happen to you on the day of judgement. Trust that God only wants the best for us, and welcomes us into His arms with abundant love and joy. He yearns for us, chases after us, and beckons us to rest in His love and mercy.
When you have these thoughts/feelings of fear regarding hell, tell the OCD to take a hike, and you're not going to try to answer the question of salvation right now. With OCD, you will never be able to ask for salvation enough times in order to put the doubt to rest; it will always be there. Accept the risk, trust in the Lord, and attempt to go about your day as normal. When we start to rely on our experiences (feelings), we are only going to fail, because with OCD, our feelings often betray us and misrepresent the truth. We OCD sufferers have this uncanny way of believing that because we feel something (or doubt something), then the threat is real.
Earlier this year, when my husband's grandfather passed away, I went through a period of serious fear of life after death. I really wanted some certainty that everything would be OK, that I'd end up in heaven and saved. As much as I yearned for that certainty, ultimately I had to accept that I wouldn't know until it was my time to go. And when that time came, what else could I do? I'd be dead! Nothing would be able to change that (unless God wanted to pull a Lazerus with me

). All I have control over is the choices I make in life - I don't have control over when I die or how long I live. So daily I try to make the best choices that I can.
I pray you will find some peace and knowledge that God will never let you escape from the palm of His loving hand.