Burning in the front part of thighs may rarely be caused by the compression of a nerve. You have not clearly said what do you mean by 'drops of sperm'. The low B12 level may not have been responsible for the burning sensation and so correction of it has not helped. Still correction needs to continue as it may be associated with many other problems including depression
. Some medications can be given by the neurologist
for the burning sensation. Nerve conduction study
to assess health of nerves will also be similarly useful.