Lump on my scalp

i have been having these strange lumps on my face and on my scalp. its like a pimple that got really big. but eventually after some time, sometimes a very long time, it heals. but then i am having these lumps on my scalp. it hurts when i touch it. sometimes it doesn't hurt, and worse is my hair is falling off. the hair on the lump area falls of everytime i touch it or pull it. when it pops, theres a liquid that comes out and also blood. unfortunately, i have felt 4 lumps on the back of my head, 2 of them already have no hair, 2 also appeared on top of my head and hair also fell out of the areas. some lumps i had popped and healed. then hair started growing back. but, at this point there too much lump, im afraid i might get bald because of this lumps, and also im scared to go under the knife just to get this our of my head. i don't really know what to do and most importantly i really don't know what it is. please tell me as soon as possible because i am really worried about this lumps. please help me. by the way im 18.