How can I love my fellow Jew as myself if I hate myself?
How do I fulfill veavta lerayacha komocha in such a case?
Most people have a favourite bad feeling like feeling sad or lonely. If you indulge in your favourite bad feeling of hating yourself then similarly you should indulge your friends with their favourite feelings which is probably something different.
The fundamental obligation of ve'ahavta le'reachah ke'mochah is to respect your friend, not to love them.
Being respected makes people feel happy and wanted, respecting them is not conditional on your love for yourself.
Practise it via the version of Hillel the Elder:
"That which is hateful to yourself, do not do to your fellow man".
Having taken that on board, perhaps address your self-hatred with his other maxims:
"If I am not for myself who is for me? And being for my own self, what am 'I'? And if not now, when?" (quoted from Perkei Avot).
First of all love your fellow as yourself is not encouraging self love. A person who focuses on themselves has no room to love others. Rather the focal point of loving another Jew is in recognizing the source of the Jewish soul which is Hashem and how all Jewish people are not really separate but make up the totality of one person.
On the one hand all Jews are holy because of their direct connection to Hashem and also seemingly different Jews who are either on a higher or lower level are all really one as one body and therefore all essential just like there are higher and lower faculties of one body but we don't disparage the lower faculties and we shouldn't disparage other Jews for their differences because in reality we are all one together. (Ch 32 of Tanya, the gemtria of the Hebrew word for heart, talks about this)
Also don't hate yourself. I hope this question was only theory
@Cashcow's answer is (excuse the bad pun) "on the money". But adding to this concept is understanding the adage properly.
The proper translation of ואהבת לרעך כמוך is "Show love to your friend as you would do to yourself." On the surface, the translation doesn't seem "novel" and in line with your question. But, there are some key words here, and you should ponder their meanings, well.
The following ideas come from 2 notable Rabbis, one of them, I believe was Rav Pesach Krohn in a speech I heard from him about 10 - 15 years ago. The other rabbi, I don't recall offhand, but, he seems to confirm a translation by Rav Shamashon Hirsch:
First know that the word אהב has the word הב meaning "give". Love is not about receiving (which seems to be a huge U.S. and worldwide concept) but giving something of yourself to someone you care about deeply.
The word used in this verse is not חבר but רעך coming from the word רעה meaning "shepherd". A shepherd leads his sheep in the right direction and protects them from danger.
So, if you love yourself, properly, you give yourself the best things in life and you are seeking your own best interest and steering yourself in the best direction possible. Most people don't seek to harm themselves, unless they have a mental condition (or they're terrorists!)
The concept, is more than just superficial love. It's about being a shepherd, protector and advocate to others. In the worst situation, you see many people who don't love themselves still can shepherd others better than themselves. I don't recommend this action all the time, but, I'm stating that this is possible.