Help, blame game

[Samk]

So this year our team organization hasn't been the best. We had decided on a design too late, and the one that was chosen hadn't been thought out at all, so 3-4 days later we re-chose, and the team decided on mine. Now I had most of the design in solidworks, I say most, not every bolt was planned out, mostly cause I'm just one person. Anyways, we go with my design, and I start building the manipulator while everyone else builds the frame, our team leader(who is a mentor) is now blaming everything on me. She says I'm way over schedule, and that I'm arguing to much. This comes from the fact that the lead build mentor has a personal problem with my design, and keeps on saying things won't work, because " I just know it won't". So I had tried to explain how everything would work, which apparently was arguing cause I was defending my design. So he ended up changing some stuff, such as frame height, and placement of things, which caused me to have to redo my math. So most of the reason that I'm late is because of the fat that items keep on changing, and that i had a 4 day late start. Now basically every meeting, I get yelled at for being to augmentative, and for causing the team to fail. And now they are trying to say that everything I have done to this point is wrong, even though I had to do it without the help of them, and the lead build mentor is who does all of the cnc machining for us, so I haven't been able to have any parts cut. And It's all apparently my fault. But if I try to explain everything, I'm told to be quiet and stop arguing, before I can even get a word out. I have had good relations with the team leader before this, and I don't know where this is coming from. Any ideas one what I can do?