No. Pelor's clerics aren't celibate
- Pelor is "a" sun god, and one of his official nicknames is "The Sun
Furthermore, Complete Divine has, for example, the following (p.117):
As befits a sun god, Pelor’s major festivals take place on solstices
and equinoxes, and many weddings and rites of passage take place
on the cusp of a new season. Blessing of the Sun-Kissed Field is a
common rite requested by farmers.
In DnD4e -- which is not the system you're asking for, but I dare
suppose that the designers haven't introduced utterly drastic changes
to such an important "NPC" -- Pelor is in a relationship with
Erathis, goddess of civilization.
- Pelor's clerics can be chaotic regarding alignment.
Based on all this (without having to dig deeper) it seems quite unlikely that Pelor would demand celibacy, or punish a cleric of his who got involved in some affairs, since he's a god considered to be a life-giving Father, to whom people pray for fertility (crops, weddings, etc), and who is himself involved in a relationship with a goddess.
Since Pelor is often described (afaik) as an advocate of moderation, too many and/or abusive/hurtful relationship are quite likely shunned by him, though.
Here's an official example
Dragon #346 has a long article on Pelor, his faith, etc. In it, there's a sample NPC called Constable Derider Fanshen (a cleric of Pelor, lv13) whose description says the following:
The Constable (as she is still called by most in the city, despite
her retirement) is unmarried, but has many male romantic interests.
This, again, shows that clerics of Pelor 1. can get married (if it weren't so, the text wouldn't have emphasized this NPC's marital status so), 2. can be involved in romantic affairs without Pelor frowning on them.
...your campaign and your DM might have other rules and concepts - and, for practical purposes, that's all that matters. So, as others have already said: ask your DM. Ask your DM whether the above holds true in the campaign you're playing in - and if not, ask for specifics, not just hints during gaming.