Hmm... Ok....
Yes, you can put the blame on work stress.. (who says you can't
anyway..?? Hehheh...
) But that certainly doesn't mean that you can't do
something about it...? And I suppose that's why you're posting it
here..? 
Let's see... Does your bf know much or feel much about this issue?
Have ya discussed it with him before...? Well, it's certainly a
good way to start..? 1st of all, let him know that you're
experiencing much stress from work and you somehow feel that it's
affecting your 'relationship' with him... In verbal words, e-mails,
letters, sms or through phone... Whichever way you're more
comfortable with...? (now, talk about the advantages of technology
advancements..?
) ENDS with this... Let him know
that you would like very much to do something about it... (in a
positive way... and it's IMPORTANT you let him know that you're not
blaming him... Cause some guys just tends to have STUPID
thoughts...
)
Some things you can do :
1. Do the relaxing things the two of you used to do together...
Enjoying the moments... And it would be NICE only if you make sure
that you have abundant time together for these occasions... Don't
rush... Do things slowly and naturally... Make SURE that none of
you is rushing off for any appointment after that...?
2. BALANCE work & life... This is a GENERAL approach... For
work stress can not only deteriorates your love life... It can also
affect your health, friends' social circle and family ties etc...
The LAST thing you want is MORE COMPLICATIONS into the matter...
Keep AFLOAT.. It's YOUR LIFE... Learn to handle and manage it
EFFICIENTLY..... 
3. Learn TECHNIQUES to relax... Aromatic therapy... GYM and
sports... Light mediation... Breathing techniques... Whatever which
would be of much help...
4. Realise it's A DIFFERENT world... WORK and AFTER work... People
tends to feel tired after a day of work... But they've probably
forgotten! Life has JUST BEGAN! Is your life all about the paper
works and jobs..?
HELL! NO, OF COURSE! Your ACTUAL life begins
AFTER your work... So are you gonna WASTE your life away...?
5. Learn to LOVE & ENJOY your job... A way to REDUCE work
stress... If you know how to manage and cope with your job scope
and duty effectively and balance the priorities and importance of
things.... Make jobs easy, make life even easier for you...?

6. ESCAPE from the 'reality'! IF all things' really SO TIGHT...
Both of you should plan for an 'escapade'...? Be it a local venture
or an overseas trip... Set aside EVERYTHING and create those
SPECIAL MOMENTS for YOURSELVES only (privated & limited...
Hehheh...
....?
Wish these advices would have been of much help? And good luck to
you? 